114 urn:lsid:arphahub.com:pub:6666f368-0968-5880-b34a-cf8d3de58b35 urn:lsid:zoobank.org:pub:A96E9753-134C-4D08-A2E3-31C66B0459C6 Fossil Record foss-rec 2193-0066 2193-0074 Pensoft Publishers 10.3897/fr.29.181268 181268 Review Article Formicidae Fossils in amber Neogene Caribbean Solenopsis (Hymenoptera, Formicidae) thief ants in Dominican amber and putative subfossil resin Bouju Valentine valentine.bouju@gmail.com https://orcid.org/0000-0003-3185-5047 1 2 Chény Cédric https://orcid.org/0000-0003-0683-2628 3 4 Gotzek Dietrich https://orcid.org/0000-0002-7374-1112 5 6 Perrichot Vincent https://orcid.org/0000-0002-7973-0430 4 Fernandez Fernando https://orcid.org/0000-0002-6862-3592 7 Barden Phillip https://orcid.org/0000-0001-6277-320X 8 Fiorentino Gianpiero https://orcid.org/0000-0001-6948-5032 8 Museum of Comparative Zoology, Harvard University, 26 Oxford Street, Cambridge, Massachusetts 02138, USA Museum of Comparative Zoology, Harvard University Cambridge United States of America https://ror.org/03vek6s52 Department of Organismic and Evolutionary Biology, Harvard University, 26 Oxford Street, Cambridge, Massachusetts 02138, USA Department of Organismic and Evolutionary Biology, Harvard University Cambridge United States of America https://ror.org/03vek6s52 State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences, 39 East Beijing Road, Nanjing 210008, China State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology and Center for Excellence in Life and Paleoenvironment, Chinese Academy of Sciences Nanjing China https://ror.org/03cz18e20 Université de Rennes, CNRS, Géosciences Rennes, UMR 6118, 263 Avenue du Général Leclerc, 35042 Rennes, Rennes, France Université de Rennes, CNRS, Géosciences Rennes Rennes France https://ror.org/015m7wh34 Department of Integrative Taxonomy and Biodiversity of Insects, Institute of Biology, University of Hohenheim, Garbenstrasse 30, 70599 Stuttgart, Germany Department of Integrative Taxonomy and Biodiversity of Insects, Institute of Biology, University of Hohenheim Stuttgart Germany https://ror.org/00b1c9541 Department of Entomology, National Museum of Natural History, Smithsonian Institution, 1000 Constitution Ave. NW, Washington, D.C. 20560, USA Department of Entomology, National Museum of Natural History, Smithsonian Institution Washington United States of America https://ror.org/01pp8nd67 Instituto de Ciencias Naturales, Universidad Nacional de Colombia sede Bogotá, Carrera 30 No. 45–03, Bogotá D.C, Colombia Instituto de Ciencias Naturales, Universidad Nacional de Colombia sede Bogotá Bogotá Colombia https://ror.org/059yx9a68 Federated Department of Biological Sciences, New Jersey Institute of Technology, Dr Martin Luther King Jr Boulevard, Newark, New Jersey 07102, USA Federated Department of Biological Sciences, New Jersey Institute of Technology New Jersey United States of America

Corresponding author: Valentine Bouju (valentine.bouju@gmail.com)

Academic editor: Florian Witzmann

 2026 24 07 2026 29 2 499 517 98145811-DBE1-5589-9790-F474160762C4 CA3C2284-747B-4D48-BF31-0EEF933BB86F 04 12 2025 14 07 2026 Valentine Bouju, Cédric Chény, Dietrich Gotzek, Vincent Perrichot, Fernando Fernandez, Phillip Barden, Gianpiero Fiorentino This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. https://zoobank.org/CA3C2284-747B-4D48-BF31-0EEF933BB86F

Solenopsis is a diverse genus of myrmicine ants with a global distribution. Several extinct species have been described but these occurrences are limited to the Palaearctic as imprint fossils. Wilson (1985, 1988) mentioned specimens of Solenopsis preserved in Dominican amber (Middle Miocene, ca. 16 Ma), though these have not been formally described. Through ethanol exposure and Raman spectroscopy, we assessed the provenance of several putative amber specimens in museum collections. We identified multiple instances of labeled amber specimens that are instead most likely subfossil copal or recent resin – these include specimens in a historical collection. Based on material with provenance and properties consistent with fossil resin, or, amber, we report five new fossil species of minor workers attributed to the genus Solenopsis: S. lamellatasp. nov., S. pilonariasp. nov., S. merenguesp. nov., S. viralatasp. nov., and S. picapicasp. nov. One of the species described, S. lamellatasp. nov., is highly aberrant, possessing a spine-like lamella on the posterior margin of the propodeum, a trait not shared with any known Solenopsis species. The discovery of these five fossil species sheds light on the biogeographic history of the genus Solenopsis. Beyond ants, these results highlight the need for caution in assuming the provenance of specimens from museum collections and commercial sources.

 Dominican amber Miocene Myrmicinae Solenopsis Introduction

The genus Solenopsis is a taxonomically challenging ant lineage. Most of the species of the genus are very uniform in their external morphology, with few attributes that highlight or separate species, such as sculpturing on the head (Solenopsis ruginodis), postpetiole width (Solenopsis globularia, Solenopsis virulens), scape length (Solenopsis pygmaea), or anterior clypeal teeth absent (Solenopsis wasmanni). Most species are monotonous in their external features, making species identification difficult (Pacheco and Mackay 2013). The genus is monophyletic (Ward et al. 2015), although we lack global phylogenies that explore their internal phylogeny (Shoemaker et al. 2006; Shreve et al. 2020). In the past the genus has been informally divided into three groups: the “fire ants”, the “thief ants”, and the “parasitic” ants (Pacheco and Mackay 2013). Of these informal groups, only the fire ants (geminata group) appear to be natural (Shreve et al. 2020); the other two conglomerates are non-monophyletic. In the past 80 years, three notable works have attempted a synthesis of parts of the genus, though all have been limited to the New World: Creighton (1930) and Trager (1991) on the New World species of the “fire ants”. Pacheco and Mackay (2013) reviewed the taxonomy of the thief ant group of Solenopsis in the New World (86 species).

In the modern fauna, more than 180 extant species of Solenopsis are described (Bolton 2025). The two most widely distributed species belong to the geminata and saevissima complexes, also known as “fire ants”. The Tropical Fire Ant, S. geminata, and the Red Imported Fire Ant, S. invicta, both native to South America, have been inadvertently introduced across the globe (Ascunce et al. 2011; Gotzek et al. 2015) and become highly invasive pest species, ranking among the most damaging invasives (Lowe et al. 2000; Holway et al. 2002). Most of the species diversity remains mainly within the Neotropical region, though much of the global diversity may be unknown due to a lack of systematic study outside of the Neotropics.

Fossil occurrences of Solenopsis are not constrained to the neotropics. The genus was first known from the Palearctic fossil record (Table 1): Förster (1891) historically described six fossil species of the extinct genus Attopsis (A. blanda, A. maxima, A. moesta, A. privata, A. superba, and A. valida) preserved as compression fossils either in the Oligocene (34–30 Ma) of France (Brunstatt, Haut-Rhin) or/and Germany (Kleinkems, Bade-Württemberg). Half a century later, the French Théobald (1937) assigned them to Solenopsis and described two additional species, S. foersteri and S. major, from the same deposits. While formally described, this material should be viewed with caution because the descriptions are based on imprints of various states of preservation and have never been the subject of revision since published. The species S. major described by Théobald was a junior primary homonym of Solenopsis basalis major Forel, (1913), according to article 60 of the International Code of Zoological Nomenclature (ICZN 1999). Özdikmen (2010) proposed to rename the species described by Théobald (1937) as S. alena. Nonetheless, more recently, Perfilieva et al. (2017) have described the fossil species S. atavinus from the Miocene shales of Yurkino in the Crimean Peninsula, based on an imprint of a gyne. From amber, the genus was completely unknown until the 1980s. The Museum of Comparative Zoology (MCZ) of Harvard University (Cambridge, USA) houses a historical collection of putative amber from Dominican origin, examined by Wilson (1985) in a study of the biogeographic evolution of West Indian ants. In that study, the presence of Solenopsis is mentioned for the first time, reporting three morphotypes: Solenopsis [sensu stricto], S. (Diplorhoptrum), and S. (Euophthalma) (Wilson 1988). But none of these morphotypes were described. Similarly, Solórzano Kraemerr (2007) recently reported workers of a Solenopsis fossil species from the Miocene Mexican amber of Simojovel, a coeval amber deposit of the Dominican amber, but this morphotype has not yet been described either.

Ethanol assay and Raman spectroscopy results. Ratio (p) denotes peak ratio values calculated as the greatest intensity values between a range of 1543-1771 and 1400–1510 cm-1; Ratio (s) denotes strict ratio of intensity at 1646 and 1450 cm-1.

Specimen Ratio (p) Ratio (s) Ethanol test Designation Notes
Colombian Copal 1.04 0.83 Fibers stuck Reference
AMNH Dominican Copal 1 0.94 0.83 Fibers stuck Reference
AMNH Dominican Copal 2 0.91 0.80 Fibers stuck Reference
AMNH-DR-10-169 N/A N/A No fibers Amber Solenopsis picapica c.f.
AMNH-DR-10-174 0.80 0.77 No fibers Amber Solenopsis picapica c.f.
AMNH-DR-10-198 N/A N/A No fibers Amber Solenopsis pilonaria c.f.
AMNH-DR-10-211 N/A N/A No fibers Amber Solenopsis
AMNH-DR-14-408 0.87 0.87 No fibers Amber Solenopsis lamellata holotype
MNHNSD FOS 18.128 0.77 0.77 No fibers Amber Solenopsis pilonaria holotype
MNHNSD FOS 18.129 N/A N/A No fibers Amber Solenopsis picapica holotype and paratypes
MNHNSD FOS 18.130 0.82 0.78 No fibers Amber Solenopsis merengue holotype
MCZ:Ent:PALE-33942 0.97 0.96 Fibers stuck Putative copal/resin Solenopsis
MCZ:Ent:PALE-33943 0.91 0.85 Fibers stuck Putative copal/resin Solenopsis
MCZ:Ent:PALE-33944 N/A N/A No fibers, tacky surface Putative copal/resin Solenopsis
MCZ:Ent:PALE-33946 0.74 0.74 No fibers Amber Solenopsis (alate)
MCZ:Ent:PALE-33947 0.80 0.80 No fibers Amber Solenopsis viralata holotype
MCZ:Ent:PALE-33949 0.92 0.95 No fibers Putative copal/resin Solenopsis
MCZ:Ent:PALE-33953 N/A N/A No fibers Poor preservation Solenopsis
MCZ:Ent:PALE-43747 N/A N/A No fibers Amber Solenopsis pilonaria c.f. labeled Monomorium
MCZ:Ent:PALE-43767 N/A N/A No fibers Poor preservation Solenopsis labeled Monomorium
IGR.DOM-003 1.00 1.05 No fibers Putative amber but commercially derived Solenopsis

Here, we propose descriptions and assignments of the original specimens of Solenopsis previously viewed and reported by Wilson (1985, 1988) and new specimens housed in two other collections. Although this material has the potential to offer key insights into neotropical ant evolution, recent findings call for a critical re-evaluation of it. A specimen labeled as Eocene-age Baltic amber in the MCZ collection was later revealed to be a sub-fossil resin, most likely East African copal, only after it was published as the first army ant from that deposit (Sosiak et al. 2023). It is not known if this material is the result of a historical misidentification or forgery, however it seems that this dubious material entered numerous collections (Boudinot et al. 2024). We therefore tested the provenance of all holotypes described in this paper via Raman spectroscopy and ethanol assays. Our formal descriptions are restricted only to material with spectral qualities that are consistent with fossil resin, or amber. Our results describe the first Solenopsis species known from fossil resin and demonstrate a need for evaluating the origins of material with limited provenance information via physical characterization.

 Methods Origin and age of the amber

Dominican amber is renowned for its rich diversity of inclusions: protozoa, bacteria, fungi, plants, invertebrates, and vertebrates (Penney 2008); and for its exceptional preservation state (Grimaldi 1996; Poinar and Poinar 1999; Grimaldi and Engel 2005). The amber is found in two main geologic units. The La Toca Formation is located in the Cordillera Septentrional in northern Hispaniola (Northern Mining District, or NMD) and the Yanigua Formation, from which the amber quantity is much reduced, is located in the Cordillera Oriental in the northeast of Hispaniola (Eastern Mining District, or EMD) (Penney 2008). The geological age of Dominican amber has long been a controversial issue. Over the past few decades, a wide variety of age estimates have been suggested, ranging from Cretaceous (Brouwer and Brouwer 1982), Late Eocene (Lambert et al. 1985, by nuclear magnetic resonance spectroscopy), Middle Eocene (Landis and Snee 1991, by Argon geochronology), Oligocene (Grimaldi 1996, by foraminifers and nannofossils), to Lower Miocene (Baroni-Urbani and Saunders 1982). Based on biostratigraphic and palaeogeographic data, Iturralde-Vinent and MacPhee (1996) attempted to resolve discrepancies in age assignments and suggested that all the inclusion-bearing amberiferous deposits of the Dominican Republic were formed in a single sedimentary basin during the late Lower Miocene to the early Middle Miocene (20–15 Ma). More recently, the age of the amber has been further constrained to approximately 16 Ma (Iturralde-Vinent 2001) by a geological dating of the sediments in which the amber deposits were encased. This estimate has been widely accepted, and an additional study (Ortega-Ariza et al. 2015) has corroborated this assessment.

 Preparation and study of the material

Repository collections (specimen provenance detailed in Table 1).

Museum of Comparative Zoology Entomology Collection of Harvard University, Cambridge, U.S.A. (MCZ); American Museum of Natural History, New York, U.S.A. (AMNH); Museo Nacional de Historia Natural ‘Prof. Eugenio de Jesús Marcano’, Santo Domingo, Dominican Republic (MNHNSD); Geological Department and Museum of the University of Rennes, Rennes, France (IGR).

We made observations, measurements, and took images using a Zeiss Axio Zoom.V16 stereomicroscope and a Nikon Digital Sight 10 camera via an SMZ25 stereoscope. We then used Helicon Focus 6.7 and Elements v6.1 to build composite images from a series of photographs taken at different focal planes. We adjusted brightness, contrast, and color balance using Adobe Photoshop CC 2017 and 2024. We used Adobe Illustrator CC 2015 and 2024 for final plate generation. Images and specimen data will be available on AntWeb (http://www.antweb.org), upon publication of the present manuscript.

We generated micro-computed tomographic (CT) scans of four of the type specimens and an additional non-type specimen using a Zeiss Xradia 510 Versa 3D X-ray microscope operated with the Zeiss Scout-and-Scan Control System software (v. 14.0.14829.38124) at the Okinawa Institute of Science and Technology Graduate University, Japan and a Zeiss Xradia 630 3D X-ray microscope operated with the Zeiss Scout-and-Scan Control System software (v. 14.0.14829.38124) at the American Museum of Natural History (AMNH), USA. We performed the scans with varying beam intensity and magnification objectives contingent on specimen size and density. We then segmented the resulting z-stack images using 3D Slicer v. 5.11. The final volume renderings were produced using MeshLab 2023.12. Not all specimens were able to be scanned successfully, and so only four of the species have corresponding CT scan data.

 Assessment of amber provenance

We developed two assays to assess the provenance of putative amber specimens. First, we tested the reactivity of specimens using ethanol. Resin polymerizes during the maturation process (Seyfullah et al. 2018). As a consequence, sub-fossil and recent resins may be uniquely soluble in ethanol to the exclusion of amber, which exhibits greater polymerization (Bai et al. 2019). We applied a single drop of 75% ethanol to each specimen and after two seconds dabbed away the ethanol using a cotton ball, noting whether or not any cotton fibers remained on the specimen surface or if the surface became sticky and tacky. We applied this test to three reference copal pieces from the Dominican Republic and Colombia as well as 16 pieces labeled as Dominican amber with Solenopsis inclusions for which we could obtain clear views of untreated surfaces or had permission to trim new surfaces.

Because copal or recent resins may be treated with additional solvents that impede ethanol reactivity, and because some forgeries constitute plastics that do not react with ethanol (Grimaldi et al. 1994), we further assessed specimen provenance via Raman spectroscopy. We obtained spectra using a Thermo Scientific DXRxi Raman Microscope at the New Jersey Institute of Technology Otto H. York Center for Environmental Engineering and Science. The microscope was equipped with a 785 nm excitation laser set to 30 mW at 10x magnification and spectra were acquired for 0.1 seconds averaged across 60 replicates. Spectra were baseline corrected under a “modpolyfit” approach and normalized by total intensity in the R package ChemoSpec 6.2 (Hanson 2025). While it is not possible to identify precise locality information via Raman spectroscopy, the ratio of intensity between peaks at 1646 and 1450 cm-1, has been associated with specimen maturation (Edwards and Farwell 1996); specifically, a ratio of intensity greater than 1 has been suggested to be correlated with subfossil resins (i.e. copal), while a ratio of less than 1 is associated with mature, fossilized resin (amber). We therefore assessed specimen provenance by calculating the ratio of intensity at these strict wavelengths (which we term the strict ratio), as well as the ratio of the highest intensity values between ranges of 1543–1771 and 1400–1510 cm-1 (peak ratio). We compared these second “peak” ratios after observing that the greatest intensity peaks were not precisely at 1646 and 1450 cm-1 in some specimens as noted by other authors (Brody et al. 2001), potentially because our sampling appears to include the first published spectra for copal from the Dominican Republic. We compiled these ratios and, after observing that Dominican copal yielded strict (0.80–0.83) and peak (0.91–0.94) ratio values well below 1, we determined that a ratio below 1 was not an appropriate cutoff for discerning between Dominican amber and Dominican copal.

 Terminology and measurements

General terminology for ant morphology is based on Bolton (1982, 1994), and we follow Wilson (1955) and Harris (1979) for the description of degrees of inclination of pilosity and surface sculpturing respectively. We took measurements directly on the amber specimens using light microscopy. In cases where it was impossible or difficult to measure directly, we took measurements using the 3D models produced from CT scanning. All measurements are expressed in mm. The measurements and indices used in this study follow Hita Garcia et al. (2017):

EL Eye length: maximum diameter of the compound eye measured in oblique lateral view.

HL Head length: maximum distance from the midpoint of the anterior clypeal margin to the midpoint of the posterior margin of the head, measured in full-face view.

HW Head width: maximum head width measured directly behind the eyes in full-face view.

PH Pronotal height: maximum height of the pronotum measured in lateral view.

PPH Postpetiole height: maximum height of the postpetiole measured in lateral view.

PPL Postpetiole length: maximum length of the postpetiole measured in dorsal view.

PPW Postpetiole width: maximum width of the postpetiole measured in dorsal view.

PTH Petiolar node height: maximum height of the petiolar node measured in lateral view from the highest median point of the node to the ventral outline. The measuring line is positioned at an orthogonal angle to the ventral outline of the node.

PTL Petiolar node length: maximum length of the dorsal face of the petiolar node from the anterodorsal to the posterodorsal angle, measured in dorsal view and excluding the peduncle.

PTW Petiolar node width: maximum width of the dorsal face of the petiolar node measured in dorsal view.

PW Pronotal width: maximum width of the pronotum measured in dorsal view.

SL Scape length: maximum straight-line length of the scape, excluding the antennal condyle.

WL Weber’s length: diagonal length of the mesosoma in lateral view from the anteriormost point of pronotal slope (excluding the collar) to the posteriormost extension of propodeal lobes.

TL Total body length (excluding the sting) HL + WL + petiolar peduncle length + PTL + PPL + 1st gastral segment length.

CI cephalic index: HW/HL × 100

SI scape index: SL/HW × 100

OI ocular index: EL/HW × 100

DMI dorsal mesosoma index: PW / WL × 100

LMI lateral mesosoma index: PH / WL × 100

LPeI lateral petiole index: PTL / PTH × 100

DPeI dorsal petiole index: PTW / PTL × 100

LPpI lateral postpetiole index: PPL / PPH × 100

DPpI dorsal postpetiole index: PPW / PPL × 100

PPI postpetiole index: PPW / PTW × 100

PTI petiolar index: PTH / PTL × 100

Height and distance of clypeal lateral teeth measured respectively from lower point of median margin of clypeus to tip of tooth and from tip to tip as in Fig. 1.

10.3897/fr.29.181268.figure1 1305ECCE-F2CA-53EC-9526-44487DB1D562

Measure of height (h) and distance (d) of clypeal lateral teeth. A. Poorly developed teeth; B. Well-developed teeth.

https://binary.pensoft.net/fig/1724143 Results Specimen provenance

All three reference copal specimens were reactive to ethanol and exhibited a tacky surface affixed with cotton fibers during assay testing (Table 1). Out of 16 non-reference specimens, three exhibited stuck cotton fibers or a tacky surface consistent with ethanol solubility. One of these, specimen MCZ:Ent:PALE-33953 was too poorly preserved to be described and so was excluded as a potential type specimen.

Copal reference specimens exhibited strict Raman ratios between 0.80–0.83 and peak ratio values between 0.91–1.04. Four specimens exhibited peak ratios greater than the lowest Dominican copal reference ratio. Of these four specimens, two were not reactive to ethanol – one housed in the MCZ (MCZ:Ent:PALE-33949) and one (IGR-DOM-003) commercially purchased specimen housed at the University of Rennes – (Fig. 2). Although Raman spectroscopy has been proposed as a method for distinguishing copal from other resins (Edwards and Farwell 1996; Rao et al. 2013), previous studies have not performed systematic assessments of Dominican amber and copal, specifically. Brody et al. (2001) examined only six Dominican amber specimens, and previous investigations establishing a putative cutoff ratio value of 1.0 did not include copal in their analysis (Winler et al. 1998, 2001; Tay et al. 1998). We therefore excluded all ethanol reactive specimens, as well as the IGR-DOM-003 specimen, which was non-reactive to ethanol but commercially derived, from taxonomic activity. However, we excluded no specimens on the basis of previously published ratio cutoff. To aid in future analyses of provenance, we provide a morphological description – but do not formally describe – one such well-preserved putative copal inclusion (see Suppl. material 1). We also provide all spectra data to assist in future determinations of provenance.

10.3897/fr.29.181268.figure2 A9A17AEE-49FF-5574-8FB6-3F705244186E

Raman spectra across specimens between wavelengths of 1400-1700 cm-1. Dotted lines designate greatest intensity value in the 1400–1510 cm-1 range, while shaded box corresponds with the relative distance between 1543-1771 and 1400–1510 cm-1 peaks for AMNH Dominican Copal 2 specimen, which represents the lowest reference intensity ratio in our sampling.

https://binary.pensoft.net/fig/1724144 Systematic Palaeontology

Class Insecta Linnaeus, 1758

Order Hymenoptera Linnaeus, 1758

Family Formicidae Latreille, 1809

Subfamily Myrmicinae Lepeletier de Saint-Fargeau, 1836 [1835]

Animalia Hymenoptera Formicidae B5DDAD0F-7D41-5421-BF00-5462FEB19A82 Solenopsis Westwood, 1840 Type species.

Solenopsis geminata (Fabricius, 1804), Roger, 1862, by subsequent designation.

 Type locality.

Central America.

 Diagnosis (worker).

Cf. Fisher and Bolton 2016. Solenopsis can mainly be distinguished from other Myrmicinae genera by the combination of antenna with 10 segments and a two-segmented club, and the median unpaired seta on anterior clypeal margin.

 Key to the new <italic><tp:taxon-name><tp:taxon-name-part taxon-name-part-type="genus" reg="Solenopsis">Solenopsis</tp:taxon-name-part></tp:taxon-name></italic> fossil species

Note: This key does not include the fossil species previously described from rock impression or compression due to the lack of reliable features available.

1 Petiolar node round or convex posteriorly; subpostpetiolar process thick and shovel-like, creating a concave cavity (A) 2
– Petiolar node straight or angular posteriorly; subpostpetiolar process thin, produced as a tooth, lip, or bulbs, not shovel-like (B) 3
2 Propodeal median spine present (A); head sub-rectangular, much longer than wide Solenopsis lamellata sp. nov.
– Propodeal median spine absent (B); head sub-quadrate, slightly longer than wide Solenopsis merengue sp. nov.
3 Petiolar peduncle elongate, about as long or longer than the petiolar node (A); subpetiolar process reduced, may form a translucent lamella; subpostpetiolar process is produced as a sharp downward-facing lip flanked by two bulbs Solenopsis picapica sp. nov.
– Petiolar peduncle short, much shorter than length of the petiolar node (B); subpetiolar process features a tooth (produced as a conspicuous anterior-facing tooth or a lamella followed by a blunt tooth); subpostpetiolar process never flanked by projections 4
4 Mediolateral portion of clypeus with prominent lateral and extralateral teeth (A); propodeal spiracle located in the posterior half of the propodeal lateral surface (C); subpetiolar process is a blunt tooth; subpostpetiolar process produced as a lamella followed by a blunt anterior-facing tooth Solenopsis pilonaria sp. nov.
– Mediolateral portion of clypeus with prominent lateral teeth, extralateral teeth absent (B); propodeal spiracle located midway to the anterior half of the propodeal lateral surface (D); subpetiolar process produced as a conspicuous anterior-facing tooth Solenopsis viralata sp. nov.
Animalia Hymenoptera Formicidae 26C5F9EB-0A3D-55A5-BC68-ED042C528EA4 Solenopsis lamellata https://zoobank.org/B6744D4F-1611-4F5B-8221-4CF6B7E69E08 sp. nov. Type material.

Holotype. AMNH-DR-14-408 worker, deposited in the American Museum of Natural History in New York City, U. S. A (Fig. 3). Preserved within a 10 mm by 8 mm section of yellow amber with internal bubbles. No synclusions.

10.3897/fr.29.181268.figure3 AB608492-79B3-50A4-ABA8-D0868E7E6E2B

Solenopsis lamellata sp. nov. from Miocene Dominican amber. Holotype AMNH-DR-14-408: A. Habitus in lateral view; B. 3D rendering of habitus in lateral view; C. 3D rendering of head in full-face view; D. 3D rendering of dorsal view; E. 3D rendering of propodeum, petiole and postpetiole in lateral view. Scale bars: 0.5 mm (A, B, D); 0.2 mm (C, E).

https://binary.pensoft.net/fig/1724145 Horizon and locality.

Early Miocene, Burdigalian (ca. 16 Ma; Iturralde-Vinent and MacPhee 1996); in amber from the Northern mines of the Santiago Province, Dominican Republic.

 Diagnosis.

Worker. With characters of the genus, plus the following unique combination: head much longer than wide; posterior margin of head rounded; scape length shorter than 2/3 of head length; anterior margin of clypeus without teeth; mandible with three developed teeth and a basal fourth. Propodeum in dorsal view with lateral margins tapered posteriorly; in lateral view dorsal and declivitous margin of subequal length, with a conspicuous upturned ridge between the dorsal and posterior faces, forming a propodeal lamella; propodeum spiracle in medio-lateral position. Petiolar peduncle about the same length as the petiolar node; petiolar node rounded dorsally, petiole in dorsal view longer than broad and longer than high in profile; petiole and postpetiole subequal in dorsal view; in dorsal view postpetiole as broad as long and in lateral view, postpetiole lower than petiole and appearing considerably smaller; subpetiolar process not forming a tooth; subpostpetiolar process shovel-like. Body setae long (longer than a2), particularly on the gaster.

 Description.

Worker.

Head. In full-face view, head subrectangular, much longer than wide, posterior margin convex; eyes small, with about 3 ommatidia in the largest diameter, anteriorly positioned; antenna 10 segmented, last two segments defining a conspicuous 2-segmented club, scape shorter than 2/3 of head length; clypeal carinae prominent, extending from the anterior border of the clypeus posteriorly between the antennal insertions clypeal carinae prominent, extending from the anterior border of the clypeus posteriorly between the antennal insertions and turn medially back around to the anterior border of the clypeus, clypeus prominently extended forward, medially notched, completely covering basal margin of mandible; lateral and extralateral clypeal teeth completely absent; mandibles with 4 conspicuous teeth, the sub-basal larger than the others.

Mesosoma. In profile, outline of promesonotum slightly convex; metanotal groove deep laterally and dorsally; in dorsal view, promesonotum subtriangular, humeral corners slightly rounded, lateral margins convex; in lateral view, propodeum dorsal margin slightly convex and about as long as declivitous margin, declivitous margin mildly concave, leading to a bulbous propodeal lobe; in dorsal view, margins tapered posteriorly, forming a lamella that separates the dorsal and posterior faces; propodeal spiracle circular, large, situated mid-length and slightly above mid-height of lateral face (mediodorsal position).

Metasoma. In lateral view, petiolar peduncle about the same length as the petiolar node, subpetiolar process present, projected as a blunt translucent lamellae; petiolar node rounded dorsally, about as long as wide; in lateral view, higher than long, with anterior face of node concave, strongly convex dorsum, posterior face oblique, ventral margin convex; postpetiole in dorsal view, semiglobular about as wide as long, similar in width to the petiole, anterior margin convex; postpetiole node rounded dorsally, and posterior margin slightly concave; subpostpetiolar process produced as a thick and shovel-like projection, creating a concave cavity; gaster lanceolate.

Sculpturing, setation and coloration. Head softly imbricate, promesonotum smooth and shining, lower margin of katepisternum carinate-rugose, metanotal suture carinate-rugose, propodeum imbricate, lateral margin of petiole and postpetiole imbricate, dorsal face of petiole and postpetiole smooth and shining, gaster smooth and shining. Head (mandible and antenna included) with sparse long erect setae, body covered in fine erect setae, gaster with very long erect setae. Body of holotype worker appears to be uniformly reddish in color with yellowish legs and antennae.

 Holotype measurements (in mm) and indices.

TL 1.794; EL 0.041; HL 0.432; HW 0.304; PH 0.158; PW 0.23; PPH 0.118; PPL 0.119; PPW 0.116; PTH 0.154; PTL 0.154; PTW 0.107; SL 0.259; WL 0.457; ATIVL .33; CI; SI; OI; DMI; LMI; LPeI; DPeI; LPpI; DPpI; PPI; PTI.

 Etymology.

The specific epithet comes from the Latin “lamellatus”, which means “flat plate” or “thin plate”, referring to the unusual median propodeal projection of that species.

 Comments.

S. lamellata sp. nov.’s middle lamella on the posterior margin of the propodeum is unique in this species, previously unknown in all Solenopsis. It might be associated with the posterior narrowing of the propodeum which differs from other species where the propodeum has a uniform width (as in practically all Myrmicinae). The possible function of this lamella structure is unknown, as well as the distinct, sharp median carinae on the anterior third of the dorsal surface of postpetiole of Typhlomyrmex prolatus (Ectatomminae) (Fernández et al. 2023). The combination of head subrectangular, antennal and clypeal configuration, and narrowing of the propodeum and propodeal lamella easily isolate S. lamellata from its congeners.

 Animalia Hymenoptera Formicidae CEAD731D-F8CB-5028-B220-336F40612E6B Solenopsis pilonaria https://zoobank.org/647DEBED-DD89-4A74-B9AC-6499A6432E45 sp. nov. Type material.

Holotype. specimen identifier MNHNSD FOS 18.128 worker, deposited in the Museo Nacional de Historia Natural “Prof. Eugenio de Jesús Marcano”, Santo Domingo, Dominican Republic (Fig. 4). Preserved within a 10 mm by 8 mm section of yellow amber with internal bubbles. Synclusions include a Dorylinae ant worker.

10.3897/fr.29.181268.figure4 029F2F63-3BBE-5D82-9F1B-86D78655A946

Solenopsis pilonaria sp. nov. from Miocene Dominican amber. Holotype MNHNSD FOS 18.128: A. Habitus in lateral view; B. 3D rendering of habitus in lateral view; C. 3D rendering of head in full-face view; D. 3D rendering of dorsal view; E. 3D rendering of propodeum, petiole and postpetiole in lateral view. Scale bars: 0.5 mm (A, B, D); 0.25 mm (C, E).

https://binary.pensoft.net/fig/1724146 Horizon and locality.

Early Miocene, Burdigalian (ca. 16 Ma; Iturralde-Vinent and MacPhee 1996); in amber from the Northern mines of the Santiago Province, Dominican Republic.

 Additional material examined.

Worker, specimen identifier MCZ:Ent:PALE-43747 [MCZ]. Worker, specimen identifier AMNH-DR-10-198 [AMNH]; Dominican Republic.

 Diagnosis.

Worker. With characters of the genus, plus the following unique combination of characters: Head subquadrate, slightly longer than wide, posterior margin straight; scape about as long as 2/3 of head length; anterior margin of clypeus with developed lateral teeth, and poorly developed extralateral teeth; distance between lateral clypeal teeth higher than five times their height; mandibles with four coarse teeth and a basal fifth. Propodeum in dorsal view with subparallel lateral margins; in lateral view dorsal and declivitous margins of subequal length, propodeum unarmed; posterodorsal position of propodeal spiracle. Petiolar peduncle shorter than the length of the petiolar node, petiolar node narrow dorsally; in dorsal view, petiole as broad as long, postpetiole broader than long and slightly broader than petiole, in lateral view, postpetiole lower than petiole; subpetiolar process produced as anterior facing tooth. Setae medium and sub-erect, with pairs of longer setae on dorsum of propodeum, petiole, and postpetiole segments.

 Description.

Worker.

Head. In full-face view, head sub-quadrate, slightly longer than wide, posterior margin convex; compound eyes oval and weakly bulging, composed by 3–4 ommatidia total, located slightly anterior to the midlength of the head, frontal carinae short; frontal lobes rounded, concealing most of the antennal sockets; antenna 10 segmented; antennal scape reaching but not surpassing the posterior margin, scape length about 2/3 of head length and longer than four times pedicel; clypeus medially with a pair of longitudinally subparallel carinae, fading posteriorly, anteriorly terminating in a pair of median teeth on the anterior clypeal margin, projected forward (clypeal lateral teeth); two smaller mediolateral teeth next to the median pair (clypeal extralateral teeth); distance between the tips of clypeal lateral teeth about five time the height of clypeal teeth from tip to lower point of median clypeal margin; median portion of clypeus raised and rather narrowly inserted between the frontal lobes, not strongly projecting forward; anterior margin of clypeus W-shaped (its extremity defined by the clypeal teeth), concave margin between the two median tips; mandibles with four conspicuous teeth and a fifth defining the basal angle; the sub-basal and apical tooth being the longest.

Mesosoma. In profile, outline of pronotum slightly convex leading to flat mesonotum; metanotal groove deep laterally and dorsally; in dorsal view, with lateral margins subparallel; in profile, dorsal margin subequal to declivitous margin and slightly rounded, meeting declivitous face at rounded angle, declivitous face convex; propodeal spiracle circular, large, located slightly upper to the midpoint of propodeum and excentered towards the declivitous margin (posterodorsal position).

Metasoma. In lateral view, petiolar peduncle shorter than the length of the petiolar node, with ventral rugosities, subpetiolar process with an anterior facing blunt tooth; petiolar node narrow dorsally, in dorsal view about as broad as long; in lateral view with weakly concave sloping anterior face, a short, flat dorsal face, and sloping to straight posterior face, ventral face convex; postpetiole nodulous, broader than long in dorsal view and slightly broader than petiole, lower than it in lateral view; subpostpetiolar process with a blunt anterior facing lip. Gaster lanceolate.

Sculpturing, setation and coloration. Holotype bicolored, head and gaster light brown contrasting with a yellow mesosoma; body rather smooth, with fine punctures on dorsum of head. Head (mandibles and antennae included), mesosoma (legs included), and metasoma with suberect setae of medium-size, about half as long as pre-apical antennomere a9; anterior margin of pronotum, dorsum of petiole and postpetiole with pairs of long setae, about as long as pre-apical antennomere a9; mandibles, antennae and legs covered by numerous short suberect setae.

 Holotype measurements (in mm) and indices.

TL 1.66; EL 0.043; HL 0.46; HW 0.36; PH 0.19; PW 0.23; PPH 0.15; PPL 0.10; PPW 0.13; PTH 0.18; PTL 0.13; PTW 0.12; SL 0.28; WL 0.53; ATIVL 0.44; CI 78; SI 78; OI 12; DMI 43; LMI 36; LPeI 72; DPeI 92; LPpI 67; DPpI 13; PPI 11; PTI 140.

 Etymology.

The species was named by students of the Universidad Autónoma de Santo Domingo (Santo Domingo, Dominican Republic). The naming refers to am everyday object from Dominican Republic. The specific epithet refers to the tool “pilón” that is used to crush and prepare chocolate or other ingredients.

 Comments.

Among Dominican amber Solenopsis, S. pilonaria sp. nov. shares most affinities with S. merengue sp. nov., although it differs from it notably in having shorter scape relative to head length, a pair of extralateral clypeal teeth, an additional mandibular tooth, and a propodeum spiracle slightly deported toward the posterior margin. It differs from S. viralata sp. nov., and S. picapica sp. nov. by having a straight posterior margin of head, different antennal configuration, less developed lateral clypeal teeth, different subpetiolar process configuration, and different pilosity configuration. It is the only species having extralateral clypeal teeth and five mandibular teeth.

Solenopsis pilonaria sp. nov. most resembled the molesta species complex, based on: antennomeres 3–7 broader than long, eyes distinctly with fewer than 12 ommatidia, bicarinate clypeus with concave median anterior margin, head somewhat quadrate to slightly elongate, postpetiole about as wide as petiole, to slightly wider in dorsal view, and fine punctures on dorsum of head. Within the molesta species complex, the body size (> 1.6 mm), fine punctures, developed clypeal teeth, oval-shaped eyes, and petiolar peduncle ventral tooth of S. pilonaria sp. nov., suggest affinities with the molesta and pollux subgroups. Yet, our species differs from previously described species from these groups by the following combination of characters: scape length, extralateral teeth, smooth mesopleuron, spiracle on posterior part of propodeum, and ventral tooth on petiolar peduncle. In Solenopsis, the mandibular teeth are normally small and close together, while in the new species they are large, coarse and further apart.

 Animalia Hymenoptera Formicidae 49F21683-E4BB-529B-BFCF-66BEF647D1C5 Solenopsis merengue https://zoobank.org/E80D2293-8643-4EE6-B193-7050741B389A sp. nov. Type material.

Holotype. Worker, specimen identifier MNHNSD FOS 18.130 [MNHNSD] (Fig. 5A–E); Dominican Republic, deposited in the Museo Nacional de Historia Natural “Prof. Eugenio de Jesús Marcano”, Santo Domingo, Dominican Republic (Fig. 5). Preserved within a 5 mm by 3 mm section of yellow amber with internal bubbles. No synclusions.

10.3897/fr.29.181268.figure5 6AFC7EF6-79D4-5271-96AB-65F80717F988

Solenopsis merengue sp. nov. from Miocene Dominican amber. Holotype MNHNSD FOS 18.130: A. Habitus in lateral view; B. 3D rendering of habitus in lateral view; C. 3D rendering of Head in full-face view; D. 3D rendering of dorsal view; E. 3D rendering of propodeum, petiole and postpetiole in lateral view. Scale bars: 0.2 mm (A – C, D); 0.1 mm (E).

https://binary.pensoft.net/fig/1724147 Horizon and locality.

Early Miocene, Burdigalian (ca. 16 Ma; Iturralde-Vinent and MacPhee 1996); in amber from the Northern mines of the Santiago Province, Dominican Republic.

 Diagnosis.

Worker. With characters of the Solenopsis genus, plus the following unique combination of characters: Head sub-quadrate, slightly longer than wide, posterior margin of head straight; scape about 2/3 of head length; anterior margin of clypeus with poorly-developed lateral teeth, with teeth height lower than a fifth of the distance separating the teeth; masticatory margin of the mandibles with 3 large, coarse teeth and a basal fourth, smaller. Propodeum in dorsal view with subparallel lateral margins; in lateral view dorsal and declivitous margins subequal, propodeal propodeum unarmed; mediodorsal position of spiracle on propodeum. Petiolar peduncle shorter than the length of the petiolar node, petiolar node rounded dorsally; in dorsal view petiole broader than long; petiole and postpetiole nodulous, postpetiole wider than petiole; in lateral view postpetiole lower than petiole and broader than long in dorsal view; subpetiolar process with a ventral tooth; subpostpetiolar process thick and shovel-like, creating a concave cavity. Body setae medium and sub-erect, with pairs of longer setae on dorsum of propodeum, petiole, and postpetiole segments.

 Description.

Worker.

Head. In full-face view, head sub-quadrate, slightly longer than wide, posterior margin straight; eyes small, with 6–7 ommatidia, located slightly in front of the mid-length of the head; frontal carinae restricted to the small frontal lobes; frontal lobes present and rather developed, concealing most of the antennal sockets; antenna 10-segmented; antennal scape bent in its basal part, not surpassing the occipital margin, about 2/3 of head length and more than four times pedicel length; median portion of clypeus slightly concave, narrowly inserted between the frontal lobe, clypeus longitudinally bicarinate, consisting of two symmetrical and sub-rectilineal carinae, each one terminating in a poorly developed tip in the anterior clypeal margin, projected forward; clypeal lateral teeth poorly developed, their height lower than a fifth of the distance that separates teeth tips; extralateral teeth absent; anterior margin of clypeus in W-shaped (its extremity defined by the lateral teeth), concave margin between the teeth; clypeus with an unpaired long seta at the midpoint of the anterior margin; mandibles with 3 conspicuous teeth and a fourth tooth defining the basal angle; the apical tooth being the longest. Subbasal and subapical teeth spaced apart.

Mesosoma. In profile, outline of pronotum convex; metanotal groove deep laterally and dorsally; propodeum in dorsal view with lateral margins subparallel; in profile, dorsal face slightly convex, about as long as declivitous face, meeting declivitous face at rounded angle, declivitous face slightly convex; propodeal spiracle large, circular, centered on upper half of propodeum (mediodorsal position).

Metasoma. In lateral view, petiolar peduncle shorter than the length of the petiolar node, subpetiolar process forming conspicuous anterior facing tooth; petiolar node rounded dorsally; in dorsal view broader than long, in lateral view anterior face convex, dorsal face strongly convex, posterior face convex. Postpetiole rounded dorsally, as wide as petiole and only slightly lower than petiole in lateral view; subpostpetiolar process with conspicuous coupled anterior facing lobes, ventrally lobes meet at strongly concave sternite. Gaster lanceolate; sting out, very elongate, its extremity ended by a beveled or at least a tapered edge.

Sculpturing, setation and coloration. Head (mandibles and antennae included), mesosoma (legs included), metasoma with suberect setae of medium-size, which seem to be especially more abundant on the head and the gaster; anterior margin of pronotum, dorsum of petiole and postpetiole with a pair of long setae; mandibles, antennae and legs covered by numerous short suberect setae. Sculpturing appears uniformly smooth.

 Holotype measurements (in mm) and indices.

TL 1.32; HL 0.37; HW 0.30; PH 0.15; PW 0.19; PPH 0.12; PPL 0.10; PPW 0.12; PTH 0.14; PTL 0.15; PTW 0.12; SL 0.22; WL 0.39; ATIVL 0.31; CI 81; SI 73; DMI 49; LMI 38; LPeI 107; DPeI 80; LPpI 83; DPpI 120; PPI 100; PTI 93.

 Etymology.

The species was named by students of the Universidad Autónoma de Santo Domingo (Santo Domingo, Dominican Republic). The naming refers to words from Dominican Republic. The specific epithet refers to the “Merengue” music and dance originating from the Dominican Republic. It is treated as a name apposition.

 Comments.

Among Dominican amber Solenopsis, S. merengue sp. nov. is most similar to S. pilonaria sp. nov., although it differs from it notably in having longer scape relative to head length, no extralateral clypeal teeth, four mandibular teeth, and a propodeum spiracle centered on upper half of propodeum and not deported toward the posterior margin. It differs from S. viralata sp. nov., and S. picapica sp. nov. in having a straight posterior margin of head, different antennal configuration, less developed lateral clypeal teeth, different subpetiolar process configuration, and different pilosity configuration. The teeth of the mandible resemble S. lamellata sp. nov., but S. merengue sp. nov. lacks the propodeal lamella, the head is rectangular and the propodeum tapers posteriorly. It is the only species having a scape longer than 2/3 of head length

Solenopsis merengue sp. nov. shares affinities with the brevicornis species complex, based on: funicular segments broader than long, eyes fewer than 12 ommatidia, bicarinate clypeus with concave median anterior margin of clypeus, head somewhat quadrate to slightly elongate, postpetiole about as wide as petiole, to slightly wider in dorsal view, and fine punctures on dorsum of head. Among the brevicornis species complex, the species mostly resembles S. brevicornis. However, it also differs from it by a longer scape, the presence of a ventral tooth on the petiolar peduncle, and a different shape of propodeum. The combination of antennal configuration, large and coarse teeth (except the basal one) and the greater height of the petiole relative to the postpetiole separates this species from other Solenopsis and most or all Formicidae.

 Animalia Hymenoptera Formicidae B17F1B42-146B-5E35-B937-09D8A5888E1D Solenopsis viralata https://zoobank.org/521F2E08-EE08-4B49-AEA9-666697747CD4 sp. nov. Type material.

Holotype. Worker, specimen identifier MCZ:Ent:PALE-33947 [MCZ] (Fig. 6); Dominican Republic, deposited in the Museum of Comparative Zoology at Harvard University in Cambridge, Massachusetts U.S.A. Preserved within an 8 mm by 3 mm section of yellow amber. No syninclusions.

10.3897/fr.29.181268.figure6 C858C4E3-5B83-5A57-BB29-55514158376C

Solenopsis viralata sp. nov. from Miocene Dominican amber. Holotype MCZ:Ent:PALE-33947: A. Habitus in lateral view; B. Head in full-face view; C. Dorsal view; D. Propodeum in lateral view; E. Petiole in dorsal view and postpetiole in lateral view. Scale bars: 0.5 mm (A, D); 0.2 mm (B, C, E).

https://binary.pensoft.net/fig/1724148 Horizon and locality.

Early Miocene, Burdigalian (ca. 16 Ma; Iturralde-Vinent and MacPhee 1996); in amber from the Eastern mines of the Hato Mayor Province, Dominican Republic.

 Diagnosis.

Worker. With characters of the Solenopsis genus, plus the following unique combination of characters: Head sub-quadrate, with posterior margin shallowly concave; scape shorter than 2/3 of head length; anterior margin of clypeus with well-developed lateral teeth, teeth higher than a fifth of the distance that separates them; mandible with three conspicuous teeth and a basal fourth. Propodeum in dorsal view with subparallel lateral margins; in lateral view, the dorsal margin visibly shorter than declivitous margin, propodeum unarmed; dorso-median position of propodeal spiracle. Petiolar peduncle about the same length as the petiolar node, petiolar node angular dorsally; in dorsal view, petiole and postpetiole nodulous, of equal width, petiole about as long as broad and postpetiole broader than long; subpetiolar process without ventral tooth. Body with suberect setae, particularly abundant on dorsum of gaster.

 Description.

Worker.

Head. In full-face view, head sub-quadrate, slightly longer than wide, posterior margin shallowly concave; compound eye, oval, and weakly bulging, inserted in the latero-dorsal margin, located slightly in front of the mid-length of the head; frontal carinae restricted to the small rounded frontal lobes; frontal lobes present and rather developed, concealing most of the antennal sockets; antenna 10 segmented; antennal scape less than 2/3 of head length but longer than four times pedicel length; median portion of clypeus raised and rather narrowly inserted between the frontal lobe; clypeus longitudinally bicarinate, consisting of two symmetrical and sub-rectilinear carinae, into frons in v shape, each one terminating in a prominent tooth in the anterior clypeal margin (clypeal lateral teeth), with concave margin between them, extralateral teeth absent; mandibles with 3 conspicuous teeth and a fourth one defining the basal angle; the apical tooth being the longest.

Mesosoma. In profile, outline of pronotum convex; metanotal groove deep laterally and dorsally; propodeum in dorsal view with lateral margins subparallel, regular carina on each side of the dorsum, from the metanotal groove to the posterior margin; in profile, dorsal face convex, shorter than declivitous face; propodeal spiracle round, centered on the upper half of propodeum (mediodorsal position).

Metasoma. In lateral view, petiolar peduncle about the same length as the petiolar node, subpetiolar process forming conspicuous anterior facing tooth; petiolar node angular dorsally, in dorsal view about as broad as long, in lateral view anterior face concave, dorsum flat, posterior face coarsely convex. Postpetiole node rounded, broader than long, as broad as petiole in dorsal view, and lower than petiole in lateral view. Gaster lanceolate.

Sculpturing, setation and coloration. Body smooth. Head (mandibles and antennae included), mesosoma (legs included), metasoma with suberect setae, mandibles, antennae and legs covered by numerous short suberect setae.

 Holotype measurements (in mm) and indices.

TL 1.8–2.0; HW 0.36; PW 0.20; PPW 0.10; PTL 0.12; PTW 0.10; SL 0.28–0.29; WL 0.47–0.50; SI 78; DMI 41; DPeI 83; PPI 100.

 Etymology.

The species was named by students of the Universidad Autónoma de Santo Domingo (Santo Domingo, Dominican Republic). The naming refers to a word used in Dominican Republic. “Viralata” is said to the dogs in the street.

 Comments.

Among Dominican amber Solenopsis, S. viralata sp. nov. is most similar to S. picapica sp. nov., although it differs from it in having shorter scape relative to head length and shorter pedicel relative to following antennomeres, but longer apical antennomere relative to the length of combined antennomeres 3–9, and a propodeum spiracle centered on upper half of propodeum and not deported toward the posterior margin. It differs from S. pilonaria sp. nov., and S. merengue sp. nov. in having a shallowly concave posterior margin of head, different antennal configuration, more prominent clypeal teeth, different subpetiolar process configuration, and no pairs of longer setae on propodeum, petiole, and postpetiole dorsum. It is the only species with dorsal margin of propodeum visibly shorter than declivitous margin.

Solenopsis viralata sp. nov. shares affinities with the molesta species complex, based on: funicular segments broader than long, eyes small but distinct of fewer than 12 ommatidia, bicarinate clypeus with concave median anterior margin of clypeus, head somewhat quadrate, postpetiole about as wide as petiole, and fine punctures on dorsum of head. Within the molesta species complex, the body size (> 1.6 mm), fine punctures, developed clypeal teeth, oval-shaped eyes, and rounded propodeum, suggests affinities with the molesta subgroup. Yet, the combination of antennal configuration, distance between lateral clypeal teeth ca. 60–65 µm, smooth mesopleuron, spiracle on mid part of propodeum, the lateral keels of the propodeum, and absence of petiolar peduncle ventral tooth separate this species from the other species in the genus and from the rest of the Formicidae.

Possible additional material of Solenopsis viralata sp. nov. MCZ:Ent:PALE-33947 does not present clear trace of dehydration or compression. There is no syninclusion in the piece containing the specimen.

 Animalia Hymenoptera Formicidae 3D93C45A-04DA-518C-9E2B-25B9913B3CCE Solenopsis picapica https://zoobank.org/6586B7D2-3A4B-4898-BD23-A523C755B61A sp. nov. Type material.

Holotype. Worker, specimen identifier MNHNSD FOS 18.129#1 [MNHNSD] (Fig. 7); Dominican Republic, deposited in the Museo Nacional de Historia Natural “Prof. Eugenio de Jesús Marcano”, Santo Domingo, Dominican Republic (Fig. 7). Preserved within a 20 mm by 15 mm piece of yellow amber with internal bubbles. Synclusions include a small termite and an Azteca ant worker.

10.3897/fr.29.181268.figure7 EDA63551-D5E4-5F3A-9B95-0F1885EB23C8

Solenopsis picapica sp. nov. from Miocene Dominican amber. Holotype MNHNSD FOS 18.129#2: A. Habitus in lateral view; B. 3D rendering of habitus in lateral view; C. 3D rendering of Head in full-face view; D. 3D rendering of dorsal view; E. 3D rendering of propodeum, petiole and postpetiole in lateral view. Paratype MNHNSD FOS 18.129#1: F. Habitus in lateral view. Paratype MNHNSD FOS 18.129#3; G. Habitus in lateral view. Scale bars: 0.5 mm (A, B, D, F, G); 0.2 mm (C, E).

https://binary.pensoft.net/fig/1724149 Horizon and locality.

Early Miocene, Burdigalian (ca. 16 Ma; Iturralde-Vinent and MacPhee 1996); in amber from the Northern mines of the Santiago Province, Dominican Republic.

 Paratypes.

3 workers, specimen identifiers MNHNSD FOS 18.129#2 (Fig. 6D), MNHNSD FOS 18.129#3, and MNHNSD FOS 18.129#4 (3 workers) [MNHNSD]; Dominican Republic.

 Additional material examined.

Worker, specimen identifier AMNH-DR-10-169 [AMNH] (Fig. 6E), Dominican Republic.

 Diagnosis.

Worker. With characters of the Solenopsis genus, plus the following unique combination of characters: Head sub-quadrate, with posterior margin shallowly concave; scape about 2/3 of head length, longer than four times length of pedicel (a2); anterior margin of clypeus with well-developed lateral teeth, lateral teeth higher than a fifth of the distance that separates them; mandible with 3 conspicuous teeth and a basal fourth. Propodeum in lateral view with subequal dorsal and declivitous margins and unarmed, and posterodorsal propodeal spiracle. Petiolar peduncle longer than length of the petiolar node, petiolar node angular dorsally; petiole in dorsal view longer than wide and longer than high in profile; postpetiole wider than long in dorsal view and broader than petiole; subpetiolar process without ventral tooth and subpostpetiolar configuration, consisting of laterally produced tubercules and a long centrally projected lip. Body with suberect setae, particularly abundant on dorsum of gaster.

 Description.

Worker.

Head. In full-face view, head sub-quadrate, slightly longer than wide, posterior margin shallowly concave; compound eyes small, containing 5–6 ommatidia, oval and weakly bulging, inserted in the latero-dorsal margin, located slightly in front of the mid-length of the head; frontal carinae restricted to the small rounded frontal lobes; frontal lobes present and rather developed, concealing most of the antennal sockets; antenna 10-segmented; antennal scape about 2/3 of head length and longer than four times pedicel length; median portion of clypeus raised and rather narrowly inserted between the frontal lobe; clypeus longitudinally bicarinate, consisting of two symmetrical and subrectilinear carinae, into frons in v shape, each one terminating in a prominent tooth in the anterior clypeal margin (clypeal lateral teeth), concave margin between the two lateral teeth, extralateral teeth absent; mandibles with three conspicuous teeth and a fourth one defining the basal angle; the apical tooth being the longest.

Mesosoma. In profile, outline of pronotum convex; metanotal groove deep laterally and dorsally; propodeum in dorsal view with subparallel lateral sides, regular carina on each side of the dorsum, from the metanotal groove to the posterior margin; in profile, dorsal and declivitous margins subequal, propodeum unarmed; propodeal spiracle located on the upper half of propodeum, excentered toward the posterior margin (posterodorsal position).

Metasoma. In lateral view, petiolar peduncle longer than length of the petiolar node, subpetiolar process reduced, sometimes forming a translucent lamella; petiolar node angular dorsally; in dorsal view, petiole longer than wide and longer than high, in profile, anterior face concave, dorsum flat, posterior face coarsely convex. Postpetiole nodulous, broader than long in dorsal view, wider than petiole, and lower than petiole in lateral view, subpostpetiolar process produced as sharp downward facing lip, flanked by two bulbs. Gaster lanceolate.

Sculpturing, setation and coloration. Body smooth. Head (mandibles and antennae included), mesosoma (legs included), metasoma with suberect setae; mandibles, antennae and legs covered by numerous short suberect setae.

 Holotype measurements (in mm) and indices.

TL 1.46; EL 0.038; HL 0.42; HW 0.33; PH 0.23; PW 0.22; PPH 0.14; PPL 0.13; PPW 0.12; PTH 0.18; PTL 0.17; PTW 0.11; SL 0.33; WL 0.55; ATIVL .30; CI 89; SI 100; OI 10; DMI 46; LMI 42; LPeI 81; DPeI 85; LPpI 136; DPpI 120; PPI 109; PTI 123.

 Etymology.

The specific epithet is a name in apposition referring to the Dominican “Locrio de pica pica”, a typical Dominican recipe similar to paella, but made with canned sardines.

 Comments.

Among Dominican amber Solenopsis, S. picapica sp. nov. is most similar to S. viralata sp. nov., although it differs from it in having longer scape relative to head length but shorter pedicel relative to following antennomeres, dorsal margin of propodeum not visibly shorter than declivitous margin, and a propodeum spiracle deported toward the posterior margin. It differs from S. pilonaria sp. nov., and S. merengue sp. nov. in having a shallowly concave posterior margin of head, different antennal configuration, more prominent clypeal teeth, different subpetiolar process configuration, and no pairs of longer setae on propodeum, petiole, and postpetiole dorsum. S. picapica sp. nov. is the only species with S. lamellata sp. nov. to have an antenna pedicel much shorter than antennomeres 3–7 combined; it is the only species with a petiole not higher than long.

Solenopsis picapica sp. nov. shares affinities with the molesta species complex, based on: funicular segments broader than long, eyes small but distinct of fewer than 12 ommatidia, bicarinate clypeus with concave median anterior margin of clypeus, head somewhat quadrate to slightly elongate, postpetiole slightly wider than petiole in dorsal view, and fine punctures on dorsum of head. Within the molesta species complex, the body size (ca. 2.0 mm), fine punctures, developed clypeal teeth, oval-shaped eyes, and rounded propodeum, suggests affinities with the molesta subgroup. Similarities are also displayed with the pygmaea species complex and more particularly with the species S. goeldii Forel, 1912 mainly for sharing a relatively short peduncle, without a ventral tooth, and with ventrally convex margin. Yet, it differs from these species by the head without abundant coarse punctures, nor abundant pilosity, with larger eyes containing 5–6 ommatidia, as opposed to 1–3. The new species differs from all previously described species by the following combination of characters: smooth mesopleuron, spiracle on posterior part of propodeum, absence of petiolar peduncle ventral tooth, and the subpostpetiolar configuration, consisting of laterally produced tubercules and a long centrally projected lip.

 Conclusion

Five Solenopsis thief ant species are described from the fossil record for the first time. All specimens are found in Dominican amber pieces, aged Miocene, but undescribed Solenopsis specimens were also confirmed from putative copal of unknown origin. The ethanol and spectroscopy analyses conducted on our material have demonstrated the urgency of testing existing and newly acquired collections to separate amber from putative copal specimens. Among the new species described, S. lamellata sp. nov., displays characters such as a propodeal spine and a middle lamella on the posterior margin of the propodeum, which are unusual among Solenopsis ants and had never been described before.

 Acknowledgements

We are greatly indebted to Stefan Cover and Crystal Maier (curators of the MCZ Entomological Collection) and Ted Schultz (Smithsonian Institution) for facilitating access to MCZ specimens, as well as to David Grimaldi and Agnieszka Pierwola for providing access to material at the AMNH. We also thank Lingfen Rao for assistance with Raman spectroscopy training at the New Jersey Institute of Technology. We would also like to thank the reviewers for their thoughtful comments, greatly improving the quality of this work.

 References Ascunce MS, Yang C-C, Oakey J, Calcaterra L, Wu W-J, Shih C-J, Goudet J, Ross KG, Shoemaker D (2011) Global Invasion History of the Fire Ant Solenopsis invicta. Science 331: 1066–1068. https://doi.org/10.1126/science.1198734 Bai F, Liang H, Qu H (2019) Structural evolution of burmese amber during petrifaction based on a comparison of the spectral characteristics of amber, copal, and rosin. Journal of Spectroscopy 2019: 6904541. https://doi.org/10.1155/2019/6904541 Baroni-Urbani C, Saunders JB (1982) The fauna of the Dominican Republic amber: the present status of knowledge. In: Transactions of the 9th Caribbean Geology Conference. Santo Domingo, Dominican Republic, 213–223. Bolton B (1982) Afrotropical species of the myrmicine ant genera Cardiocondyla, Leptothorax, Melissotarsus, Messor and Cataulacus (Formicidae). Bulletin of the British Museum (Natural History) 45: 307–370. Bolton B (1994) Identification guide to the ant genera of the world. Harvard University Press, Cambridge, USA, 222 pp. Bolton B (2025) An online catalog of the ants of the world. https://antcat.org [accessed Nov. 07, 2025] Boudinot BE, Bock BL, Weingardt M, Tröger D, Batelka J, Li D, Richter A, Pohl H, Moosdorf OT, Jandausch K, Hammel JU (2024) Et latet et lucet: Discoveries from the Phyletisches Museum amber and copal collection in Jena, Germany. Deutsche Entomologische Zeitschrift 71: 111–176. Brody RH, Edwards HGM, Pollard AM (2001) A study of amber and copal samples using FT-Raman spectroscopy. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 57: 1325–1338. https://doi.org/10.1016/S1386-1425(01)00387-0 Brouwer SB, Brouwer PA (1982) Geología de la región ambarífera oriental de la República Dominicana. In: Transactions of the 9th Caribbean Geology Conference. Santo Domingo, Dominican Republic, 305–322. Creighton WS (1930) The new world species of the genus Solenopsis (Hymenop. Formicidae). Proceedings of the American Academy of Arts and Sciences 66: 39–152. https://doi.org/10.2307/20026320 Edwards HGM, Farwell DW (1996) Fourier transform-Raman spectroscopy of amber. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 52: 1119–1125. https://doi.org/10.1016/0584-8539(95)01643-0 Fernández F, Fiorentino G, Castro D (2023) A new species of Typhlomyrmex from Colombia, re-description of the worker of T. clavicornis Emery, description of the worker of T. prolatus Brown, and key of known species (Hymenoptera, Formicidae). Journal of Hymenoptera Research 96: 579–597. https://doi.org/10.3897/jhr.96.103219 Fisher BL, Bolton B (2016) Ants of Africa and Madagascar: A Guide to the Genera. Univ of California Press, 514 pp. Förster B (1891) Die Insekten des “Plattigen Steinmergels” von Brunstatt. Strassburger Druckerei und Verlagsanstalt, 290 pp. Gotzek D, Axen HJ, Suarez AV, Helms Cahan S, Shoemaker D (2015) Global invasion history of the tropical fire ant: a stowaway on the first global trade routes. Molecular Ecology, 24: 374–388. http://doi.wiley.com/10.1111/mec.13040 Grimaldi D, Engel MS (2005) Evolution of the Insects. Cambridge University Press, 788 pp. Grimaldi DA (1996) Amber: Window to the past. Abrams and American Museum of Natural History, New York, USA, 216 pp. Grimaldi DA (1996) The Age of Dominican Amber. In: Amber, Resinite, and Fossil Resins. ACS Symposium Series. American Chemical Society, 203–217. https://doi.org/10.1021/bk-1995-0617.ch011 Grimaldi DA, Shedrinsky A, Ross A, Baer NS (1994) Forgeries of Fossils in “Amber”: History, Identification and Case Studies. Curator: The Museum Journal 37: 251–274. https://doi.org/10.1111/j.2151-6952.1994.tb01023.x Hanson B (2025) ChemoSpec: Exploratory Chemometrics for Spectroscopy. R package version 6.3.0. https://bryanhanson.github.io/ChemoSpec/ Harris RA (1979) A glossary of surface sculpturing. Occasional Papers of the Bureau of Entomology of the California Department of Agriculture 28: 1–31. Hita Garcia F, Mbanyana N, Audisio TL, Alpert GD (2017) Taxonomy of the ant genus Nesomyrmex Wheeler (Formicidae, Myrmicinae) in the Afrotropical region, with a review of current species groups and description of a new species of the N. angulatus group from Mozambique. European Journal of Taxonomy 258: 1–31. https://doi.org/10.5852/ejt.2017.258 Holway D, Lach L, Suarez A, Tsutsui N, Case T (2002) The causes and consequences of ant invasions. Annual Review of Ecology and Systematics, 33: 181–233. https://www.annualreviews.org/content/journals/10.1146/annurev.ecolsys.33.010802.150444 ICZN (1999) International Code of Zoological Nomenclature. Fourth Edition. The International Trust for Zoological Nomenclature, London, 1–306. Iturralde-Vinent MA (2001) Geology of the amber-bearing deposits of the Greater Antilles. Caribbean Journal of Science 37(3–4): 141–167. Iturralde-Vinent MA, MacPhee RDE (1996) Age and Paleogeographical Origin of Dominican Amber. Science 273: 1850–1852. https://doi.org/10.1126/science.273.5283.1850 Lambert JB, Frye JS, Poinar Jr GO (1985) Amber from the Dominican Republic: Analysis by Nuclear Magnetic Resonance Spectroscopy. Archaeometry 27: 43–51. https://doi.org/10.1111/j.1475-4754.1985.tb00345.x Landis GP, Snee LW (1991) 40Ar/39Ar systematics and argon diffusion in amber: implications for ancient earth atmospheres. Palaeogeography, Palaeoclimatology, Palaeoecology 97: 63–67. https://doi.org/10.1016/0031-0182(91)90182-Q Lowe S, Browne M, Boudjelas S, De Porter M (2000) 100 of the World’s Worst Invasive Alien Species: A selection from the Global Invasive Species Database. IUCN. http://www.issg.org/booklet.pdf Ortega-Ariza D, Franseen EK, Santos-Mercado H, Ramírez-Martínez WR, Core-Suárez EE (2015) Strontium Isotope Stratigraphy for Oligocene-Miocene Carbonate Systems in Puerto Rico and the Dominican Republic: Implications for Caribbean Processes Affecting Depositional History. The Journal of Geology 123: 539–560. https://doi.org/10.1086/683335 Özdikmen H (2010) New names for some preoccupied specific and subspecific epithets in the family Formicidae (Hymenoptera). Munis Entomology and Zoology 5: 986–1000. Pacheco JA, Mackay WP (2013) The systematics and biology of the New World thief ants of the genus Solenopsis (Hymenoptera: Formicidae). Edwin Mellen Press, Lewiston, New York, USA, 501 pp. Penney D (2008) Dominican Amber Spiders: A Comparative Palaeontological-neontological Approach to Identification, Faunistics, Ecology and Biogeography. Siri Scientific Press, 178 pp. Perfilieva KS, Dubovikoff DA, Dlussky GM (2017) Miocene ants (Hymenoptera, Formicidae) from Crimea. Paleontological Journal 51: 391–401. https://doi.org/10.1134/S0031030117040098 Poinar GO, Poinar R (1999) The Amber Forest: A Reconstruction of a Vanished World. Princeton University Press, 302 pp. Rao Z, Dong K, Yang X, Lin J, Cui X, Zhou R, Deng Q (2013) Natural amber, copal resin and colophony investigated by UV-VIS, infrared and Raman spectrum. Science China Physics, Mechanics and Astronomy 56: 1598–1602. https://doi.org/10.1007/s11433-013-5144-z Seyfullah LJ, Beimforde C, Dal Corso J, Perrichot V, Rikkinen J, Schmidt AR (2018) Production and preservation of resins – past and present. Biological Reviews 93: 1684–1714. https://doi.org/10.1111/brv.12414 Shoemaker DD, Ahrens ME, Ross KG (2006) Molecular phylogeny of fire ants of the Solenopsis saevissima species-group based on mtDNA sequences. Molecular Phylogenetics and Evolution 38: 200–215. https://doi.org/10.1016/j.ympev.2005.07.014 Shreve S, Achury R, Johnson K, Suarez A, Gotzek D (2020) Multi-Locus Molecular Phylogeny of Solenopsis (Hymenoptera: Formicidae). BioRxiv 2020.06.05.136945. https://doi.org/10.1101/2020.06.05.136945 Solórzano Kraemer M (2007) Systematic, palaeoecology, and palaeobiogeography of the insect fauna from Mexican amber. Palaeontographica Abteilung A: Palaozoologie 282: 1–133. https://doi.org/10.1127/pala/282/2007/1 Sosiak CE, Borowiec ML, Barden P (2023) Retraction: An Eocene army ant. Biology Letters 19: 20230059. https://doi.org/10.1098/rsbl.2023.0059 Tay TS, Shen ZX, Yee SI (1998) On the identification of amber and its imitations using Raman spectroscopy: preliminary results. Australian Gemmologist, 20(3): 114–123. Théobald N (1937) Les insectes fossiles des terrains oligocènes de France. Imprimerie G. Thomas. Trager JC (1991) A revision of the fire ants, Solenopsis geminata group (Hymenoptera: Formicidae: Myrmicinae). Journal of the New York Entomological Society 99: 141–198. Ward PS, Brady SG, Fisher BL, Schultz TR (2015) The evolution of myrmicine ants: phylogeny and biogeography of a hyperdiverse ant clade (Hymenoptera: Formicidae). Systematic Entomology 40: 61–81. https://doi.org/10.1111/syen.12090 Wilson EO (1955) A monographic revision of the ant genus Lasius. Bulletin of the Museum of Comparative Zoology 113: 1–201. Wilson EO (1985) Invasion and Extinction in the West Indian Ant Fauna: Evidence from the Dominican Amber. Science 229: 265–267. https://doi.org/10.1126/science.229.4710.265 Wilson EO (1988) The biogeography of the West Indian ants (Hymenoptera: Formicidae). In: Zoogeography of Caribbean Insects. Cornell University Press, Ithaca, New York, USA, 214–230. Winler W, Kirchner EC, Musso M, Asenbaum A (1998) Untersuchungen an fossilen und rezenten Harzen mittels Raman-Spektroskopie. Mitteilungen der Österreichischen Mineralogischen Gesellschaft 143: 398401. Winler W, Kirchner EC, Asenbaum A, Musso M (2001) A Raman spectroscopic approach to the maturation process of fossil resins. Journal of Raman spectroscopy 32(1): 59–63. Additional information Conflict of interest

The authors have declared that no competing interests exist.

 Ethical statement

No ethical statement was reported.

 Artificial Intelligence (AI) use

The authors accept full responsibility for the content of the manuscript, including the disclosure of any use of AI.

No AI tools were used in the preparation of this manuscript.

 Funding

This research was supported by the Ernst Mayr grant for collection study of the Museum of Comparative Zoology (to V.B.) and National Science Foundation DEB CAREER grant #2144915 (to P.B.).

 Author contributions

VB, PB, VP, and GF contributed to project conceptualization; VB, GF, and PB developed and implemented ethanol assays; GF and PB performed Raman spectroscopy data collection and analysis; VB and GF imaged specimens; VB, CC, DG, FF and GF contributed to taxonomic descriptions; VB developed the taxonomic key; VB, CC, PB, and GF wrote the original manuscript; all authors contributed to manuscript review and editing.

 Author ORCIDs

V. Bouju https://orcid.org/0000-0003-3185-5047

C. Chény https://orcid.org/0000-0003-0683-2628

D. Gotzek https://orcid.org/0000-0002-7374-1112

V. Perrichot https://orcid.org/0000-0002-7973-0430

F. Fernandez https://orcid.org/0000-0002-6862-3592

P. Barden https://orcid.org/0000-0001-6277-320X

G. Fiorentino https://orcid.org/0000-0001-6948-5032

 Data availability

All of the data that support the findings of this study are available in the main text or Supplementary Information.

 Supplementary materials 10.3897/fr.29.181268.suppl1 4B309588-43A1-51A7-9A51-893F0D6B0561

Supplementary description of a Solenopsis specimen from putative copal

docx

Taxonomical description of an additional Solenopsis specimen from putative copal identified through Raman spectroscopy.

 https://binary.pensoft.net/file/1724154 This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Valentine Bouju, Cédric Chény, Dietrich Gotzek, Vincent Perrichot, Fernando Fernandez, Phillip Barden, Gianpiero Fiorentino 10.3897/fr.29.181268.suppl2 959C42E1-6196-50BC-8308-0E40CC2D111C

Raman spectra

zip

 https://binary.pensoft.net/file/1724155 This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Valentine Bouju, Cédric Chény, Dietrich Gotzek, Vincent Perrichot, Fernando Fernandez, Phillip Barden, Gianpiero Fiorentino 10.3897/fr.29.181268.suppl3 842A704E-1FB4-58EF-8D29-AFE22CBFC72B

Traducción de la información principal

docx

 https://binary.pensoft.net/file/1724156 This dataset is made available under the Open Database License (http://opendatacommons.org/licenses/odbl/1.0). The Open Database License (ODbL) is a license agreement intended to allow users to freely share, modify, and use this Dataset while maintaining this same freedom for others, provided that the original source and author(s) are credited. Valentine Bouju, Cédric Chény, Dietrich Gotzek, Vincent Perrichot, Fernando Fernandez, Phillip Barden, Gianpiero Fiorentino