A. Approximate geographic position of localities containing Marcopoloichthys furreri sp. nov., indicated with red circles; B. Stratigraphy of the Silvreta Nappe with special emphasis of the Prosanto Formation and distribution of faunas and floras. Abbreviated and slightly modified from Furrer (2019: fig. 11).

Marcopoloichthys furreri sp. nov. in lateral view. A. Holotype, PIMUZ A/I 2886; B. Paratype BNM 201166; C. Paratype PIMUZ A/I 3209. Scale bars: 5 mm. Photographs in A and B were taken by T. Scheyer and in C by C. Radke.

Marcopoloichthys furreri sp. nov. in lateral view. A. Paratype PIMUZ A/I 1958; B. Paratype PIMUZ A/I 2841. Scale bars: 5 mm. Photographs were taken by C. Radke.

Marcopoloichthys furreri sp. nov. A. Photograph of right side of the skull roof of paratype PIMUZ A/I 2887 (photograph was taken by C. Radke); B. Interpretative drawing. Abbreviations: a.cer, anterior ceratohyal; a.na, accessory nasal bone; ang, angular; asp, autosphenotic; cl, cleitrum; de, dentary; ect, ectopterygoid; exc, extrascapular; hh, hypohyal; iop, interopercle; mx, maxilla; na, nasal bone; mc, mandibular canal; met, mesethmoid; mx, maxilla; pa[=fr], parietal [= frontal] bone; op, opercle; orbs, orbitosphenoid; pal, palatine; p.cer, posterior ceratohyal; par, parasphenoid; pcl, postcleitra 1–3; pec.f, pectoral fin; pmx, premaxilla; pop, preopercle; ppa+dpt [= pa + dpt], postparietal + dermopterotic bone; qu, quadrate; sang, surangular; scl, supracleithrum; sop, subopercle; sy, symplectic; vo, vomer; ?, uncertain or unknown. Scale bars: 5 mm.

Marcopoloichthys furreri sp. nov. in lateral view illustrating some cranial bones in paratype PIMIZ A/I 2887. A. Cranium and pectoral girdle and fin in lateral view; photograph was taken by T. Scheyer; B. Skull roof bones illustrating ornamentation; C. Upper jaw bones; ornamentation on bones is damaged. Abbreviations: a.na, accessory or additional nasal bone; a.pl, anterior pit-line; exc, extrascapular; met, mesethmoid; m-pl, middle pit-line; mx, maxilla; na, nasal bone; pa[=fr], parietal [= frontal] bone; pmx, premaxilla; ppa+dpt [= pa + dpt], postparietal + dermopterotic bone; ptt, posttemporal. Scale bars: 1 mm.

Marcopoloichthys furreri sp. nov. Anterior region of skull roof of holotype, PIMUZ A/I 2886. A. Photograph; it was taken by T. Scheyer; B. Interpretative drawing. Abbreviations: a.na, accessory or additional nasal; met, mesethmoid; na, nasal bone; ro.c, rostral cartilage. Scale bars: 2 mm.

Marcopoloichthys furreri sp. nov. Restorations of head in lateral view. Heads reversed to the left. A. Fish during rest, based mainly on specimens PIMUZ A/I 1958, PIMUZ A/I 2841, PIMUZ A/I 2886; and BNM 201166; B. Fish during feeding, based mainly on specimen PIMUZ A/I 1958, PIMUZ A/I 2887; and BNH 201166. Abbreviations: a.cer, anterior ceratohyal; a.na, accessory or additional nasal bone; ant? antorbital?; asp, autosphenotic; cl, cleitrum; clv, clavicle; de, dentary or dentosplenial; dsp, dermosphenotic; ect, ectopterygoid; ent, entopterygoid; exc, extrascapular; hh, hypohyal; io1–5, infraorbitals 1–5; iop, interopercle; lat.e, lateral ethmoid; met, mesethmoid; mx, maxilla; na, nasal bone; op, opercle; pa [=fr], parietal bone [=frontal bone]; par, parasphenoid; ppa+dpt [= pa+dpt], postparietal bone + dermopterotic [= parietal bone + dermopterotic]; p.cer, posterior ceratohyal; pcl 1–3, postcleithrum 1–3; pmx, premaxilla; pop, preopercle; qu, quadrate; sang, surangular; s.ap, serrated appendage; scl, supracleithrum; sob, suborbital; sy, symplectic; vo, vomer. Scale bars: 1 mm.

Marcopoloichthys furreri sp. nov., partially preserved cranium and pectoral girdle and fins in latero-ventral view of paratype, PIMUZ A/I 2841. Abbreviations: ang+ar+rar, angular+articular+retroarticular; b.io, broken infraorbital bones; b.arc?, broken branchial arches?; b.r.cl, broken anterior part of right cleithrum; b.qu, broken quadrate; b.skr, broken skull roof bones; cor?, coronoid?; d.pecr, displaced pectoral rays of left fin; hy, hyomandibula; iop, interopercle; l.cl, left cleithrum; l.de, left dentary; l.pop, left preopercle; l.qu, left quadrate; l.sang, left surangular; l.sop, left subopercle; l.sy, left symplectic; orn, ornaments; pmx, premaxilla; pr, ventral process of lower jaw; r. cl, right cleitrum; r.de, right dentary; r.mx, right maxilla; r.op, right opercle; r.pop, right preopercle; r.sang, right surangular; sap, serrated appendage; spc, space; sy, symplectic; ?, unidentified element. Scale bar: 1 mm.

Marcopoloichthys furreri sp. nov., illustrating a lateral view of the abdominal or precaudal region of the vertebral column and associated elements and the dorsal fin and endoskeletal support (paratype PIMUZ A/I 1958). Small arrows point to the epineural processes. Abbreviations: aptg, 1^st anal pterygiophore or proximal radial; dptg, dorsal pterygiophores or proximal radials; int.d, interdorsal arcocentrum; int.v, interventral arcocentrum; l.dptg, last dorsal pterygiophore; pap, parapophyses; sc?: scale or scute?; sncar, supraneural carrier; sn1–8, supraneurals 1–8; 1^st cv?, first caudal vertebra?; 1^stdptg, first dorsal pterygiophore or fused proximal radials. Scale bar: 1 mm.

Marcopoloichthys furreri sp. nov., illustrating part of the pectoral girdle and fin (paratype PIMUZ A/I 2888). Abbreviations: b.ry, broken ray; cl, cleithrum with antero-ventral part broken; cor?, coracoid?; d.ra, distal radials; p.ra, proximal radials; scp?, scapula?; 1^st pecr, first pectoral ray. Scale bars: 1 mm.

Marcopoloichthys furreri sp. nov., illustrating the dorsal, anal, and pelvic fins and associated structures (paratype PIMUZ A/I 2841). Abbreviations: a.fr, anal fin rays; a.prra, anal proximal radials; bp.fr, broken pelvic rays; b.nsp, broken neural spines; c.dpra, compound dorsal proximal radial element; d.fr, dorsal fin rays; ha, haemal arch; ha+sp, haemal arch plus spine; l.dpra, last dorsal proximal radial; na, neural arch; na+sp, neural arch plus spine; n.sp, neural spine; p.fr, pelvic rays; p.pl, pelvic plate or basipterygium; sc, scales. Scale bar: 1 mm.

Marcopoloichthys furreri sp. nov., illustrating the dorsal, anal, and pelvic fins and associated structures (holotype PIMUZ A/I 2886). Oblique lines represent damaged areas. Abbreviations: a.fr, anal fin rays; a.prra, anal proximal radials; c.dpra, compound dorsal proximal radial element; d. dra, distal dorsal radial; d.fr, dorsal fin rays; ha+sp, haemal arch plus spine; int.d, interdorsal element; int.v, interventral element; l.aprra, last anal proximal radial; l.dpra, last dorsal proximal radial; m.dra?, middle dorsal radial; na+sp, neural arch plus spine; sc, scales; 1^st aprra, first anal proximal radial; 1^st ha, first haemal arch. Scale bar: 1 mm.

Marcopoloichthys furreri sp. nov., illustrating the caudal fin and its endoskeleton. A. Photograph of holotype, PIMUZ A/I 2886; photograph was taken by T. Scheyer; B. Drawing of endoskeleton. Abbreviations: da, dorsal arcocentra; H1–5, hypurals 1–5; hsPU2–4, haemal spine of preural centra 2–4; int, interhaemal; PH, parhypural ot haemal spine of preural centrum 1; nsPU1–3, neural spine of preural centra 1–3; UN, uroneurals; va, ventral arcocentra. Small arrows point to a series of anterior processes. Scale bars: 1 mm.

Marcopoloichthys furreri sp. nov., illustrating the caudal fin and its endoskeleton. A. paratype PIMUZ A/I 2841; area with oblique lines represent a damaged region; B. paratype PIMUZ A/I 1958. Abbreviations: a.f, accessory fulcra; d.sc, dorsal caudal scute; e.bfu, epaxial basal fulcra; h.bfu, hypaxial basal fulcra; h.ff, hypaxial fringing fulcra; hsPU4, haemal spine of preural vertebra 4; H1–3, hypurals 1–3; nsPU1, 4, neural spine of preural vertebrae 1, 4; PH, parhypural; pr.r1–2, procurrents rays 1–2; UN, uroneurals; v.sc, ventral caudal scute; 1^stPR, first principal caudal ray; 20^thPR, principal caudal ray numbered 20; 21^stPR, principal caudal ray numbered 21; ?, broken bases of hypurals 4 and 5? Scale bars: 1 mm.

Hypothesis of phylogenetic relationships of Marcopoloichthys furreri sp. nov. among neopterygians based on 138 characters and three outgroup taxa. Strict consensus tree of 84 most parsimonious trees: three length 464 steps, consistency index (CI) = 0.3491 and retention index (RI) = 0.6696. An asterisk identifies a uniquely derived character. Node A (crown Neopterygii) is supported by the following synapomorphies: supraorbital bone present; supramaxilla present; expanded dorsal lamina in the maxilla lost (*); nasal bones joined in midline; interopercle present; supracleithrum nearly as deep as posterior margin of opercle (Ch. 102[0]); no segmented procurrent rays in dorsal lobe of caudal fin (Ch. 109[0]); and lateral line scales as deep as, or slightly deeper than, those scales above and below (Ch. 124[0]). Node B (Teleosteomorpha): supraoccipital present (*); mobile premaxilla present (*); two supramaxillae present (*); vomers fused in adults into a single bone (*); elongated posteroventral process of quadrate present (*); uroneural(s) present (*); cycloid type of scales present (*); and leading margins of the caudal fins formed by the first and last principal rays (*). Homoplasies supporting this node are: basipterygoid process absent; internal carotid foramen on parasphenoid present; single supraorbital bone; suture between opercle and subopercle greatly inclined; origin of dorsal fin slightly posterior or just in front to pelvic fin origin; and fringing fulcra absent on pectoral fins.

Hypothesis of phylogenetic relationships of Marcopoloichthys furreri sp. nov. among crown neopterygians based on 132 characters and three outgroup taxa. Strict consensus tree of two most parsimonious trees: three length 374 steps, consistency index (CI) = 0.4599 and retention index (RI) = 0.7534. An asterisk identifies a uniquely derived character. Teleosteomorphs (Node C) are supported by the following synapomorphies: foramen for glossopharyngeal nerve placed in prootic or prootic-exoccipital suture (*); four pectoral proximal radials present (*); olfactory organ with accessory nasal sacs (*); craniotemporal muscle present (*); heart with two arterial valves (in the conus arteriosus) present (]*); muscles at the basal arteria (ventral aorta) absent (*); propterygium fused with first pectoral-fin ray; dorsal or epaxial leading margin of caudal fin with basal fulcra; and quadratojugal absent (Ch.127[1]). Node D is supported by two synapomorphies: supramaxilla or most posterior supramaxilla dorsal to maxilla and mid-caudal centra (adults) with diplospondylous centra. For other nodes see text and Arratia et al. (2021).