Denwa Formation (Middle Denwa Formation).

Anisian, Middle Triassic.

Purtala village, Madhya Pradesh, Central India (22°35'38.6"N, 78°32'17.0"E).

ISI A 54, a near complete skull (Fig. 2).

A posterior portion of skull found near Kohpani village (ISI A 207; Fig. 3), nearly complete left mandible near Jhirpa village (ISI A 208; Figs 3, 4), vertebral elements (ISI A 218 to 225, 226a and b, 227 to 234; Figs 5, 6), ribs (ISI A 235, 238 to 266; Fig. 7), cleithra (ISI A 275 to 280; Fig. 8), interclavicles and clavicles (ISI A ISI A 267, 268, 272 to 274; Fig. 9), Ulnae (ISI A 182/3, 182/4, 281, 282; Fig. 10), ilium (ISI A 283; Fig. 11), femur (ISI A 284; Fig. 12) and fibula (ISI A 285, Fig. 13). The postcranial bones are mostly fragmentary and collected from the villages of Purtala, Jhirpa and Kohpani.

Synapomorphies with Mastodonsauridae.

Pre-orbital part of skull (snout) elongated with orbits placed at the posterior half of the dorsal skull roof; orbital margins raised above the dorsal surface of the skull roof; posterolateral corners of the cheek anterior to the level of the posterior edge of the tabular horns; well-developed zone of intensive growth on the preorbital and cheek region of the skull; infraorbital sensory canal forms a Z-shaped loop on the lacrimal bone, the lacrimal flexure; deeply incised otic notch; occipital condyles anterior to quadrate condyles; well-developed, lappet-like tabular horns which are partly supported from below by muscular cristae from the paroccipital process; elongated preorbital projection of the jugal, extending to the lateral border of the snout; supratemporal bone excluded from the border of the otic notch; postorbital antero-laterally expanded (‘hooked’); crista muscularis of the parasphenoid levels with the posterior border of the pterygoid-parasphenoid suture; unbroken chain of teeth on the vomer-palatine-ectopterygoid series; occipital face of the pterygoid bears a tall, narrow, crest-like flange of bone, the oblique ridge of the pterygoid; posttemporal fenestra triangular in shape; mandible with an antero-posteriorly expanded symphysis; a short accessory sensory sulcus dorsal to the oral sulcus present.

Synapomorphies with Cherninia sp.

Pterygoid-parasphenoid suture short, less than the width of the corpus of the parasphenoid; occiput moderately shallow; skull margins moderately concave lateral to the orbits so that the cheek region is flared; prefenestral division of the palate (the region of the palate anterior to the interpterygoid vacuities) markedly elongated; anterior palatal vacuity paired but set in an oval depression so that the vacuities lie below the plane of the palate; elongated and broad snout so that parts of the anterior lateral margin of the skull on both sides are almost parallel to each other; skull roof with conspicuous, paired, forked ridges anterior to the orbits; anterior rim of the otic notch angular; temporal sensory canal extending posteriorly to the tips of the tabular horns; internal nares (choanae) are placed extremely far forward with respect to the interpterygoid vacuities.

Cherninia denwai can be distinguished from Cherninia megarhina, the second known species of Cherninia, by short and narrow postparietals, the presence of a septomaxilla, both anteriorly and posteriorly pointed interpterygoid vacuities, lack of parasphenoid groove, lack of occipital sensory canal, posteriorly directed and distally recurved tabular horns, the deeply concave occipital margin of the skull and the posteriorly broad otic.

Autapomorphies of Cherninia denwai

Skull margins moderately concave lateral to the orbits such that the cheek region is flared; elongated and moderately broad snout; lateral margins of the middle part of the skull anteromedially aligned. The skull roof has conspicuous, paired and forked ridges anterior to the orbits on both sides of the skull. Anterior rim of the otic notch angular (40–60 degrees), tabular horns posteriorly directed and recurved distally, postparietals antero-posteriorly compressed and narrow, deeply concave occipital margin of skull, well expressed lateral line sensory canals, septomaxilla present (Mukherjee and Sengupta 1998). The pterygoid-parasphenoid suture is short and the interpterygoid vacuities pointed both anteriorly and posteriorly. The skull table is shallow, the region of the palate anterior to the interpterygoid vacuities is elongated, anterior palatal vacuity paired but set in an oval depression so that the vacuities lie below the plane of the palate, cultriform process merges with the vomers and the occiput is moderately shallow. The mandible is slender and long (the largest measuring almost 96 cm in length), distinct post glenoid area (PGA) is present, hamate process of prearticular is well developed. It is pointed and sharp and its height is almost equal to the length of the PGA. The labial wall of adductor chamber is dorsally horizontal, prearticular is separated from splenial by dentary and coronoid series, glenoid facet lies below the dorsal surface of dentary.

Osteology. Skull roof (Figs 2, 3). The detailed osteological description of the dorsal part of the skull roof is as follows:

Premaxillae. The anterior-most rim of the snout is formed by the premaxillae. The premaxillae suture with the maxillae laterally, with the nasals posteriorly, and form the anteromedial part of the nasal rim. In ventral view, they contact the vomers posteriorly, the maxillae laterally, and form the anterior rim of the anterior palatal vacuity. The ornamentation is made up of pits and grooves (Figs 2, 3).

Maxillae. The anterior one-third of the lateral skull margin is formed by the maxillae, commencing from the posterolateral rim of the nares. Septomaxillae were figured by Mukherjee and Sengupta (1998), however, they are ill-preserved. Anteriorly, the maxillae are sutured with the premaxillae, medially by the nasals and the lacrimals, and posteriorly by the jugals. In ventral view, the maxillae border the premaxillae anteromedially, and suture medially with the vomers and the palatines. The anterolateral rim of the choanae is formed by the maxillae. Very faint pit and groove ornamentation is present in the anterior part (Figs 2, 3).

Nasal. The nasals are quite broad, and form a major part of the anterior skull roof medially (Figs 2, 3). They contact the premaxillae anteriorly. The nasals form a triple junction posteriorly, contacting the frontals posteromedially and the prefrontals posterolaterally. The nasals are bordered by the maxillae behind the nares and contact the lacrimals laterally. The nasals form the posteromedial rims of the nares. Pit and groove ornamentation is present in the anterior-most part and ridge and furrow ornamentation in the posterior part.

Lacrimal. The lacrimals are tear-drop shaped, suturing with the maxillae anterolaterally, the nasal medially, the prefrontal posteriorly, and the jugal posterolaterally (Figs 2, 3). Pit and groove ornamentation is present in the anterior part and ridge and furrow ornamentation in the posterior part. The lacrimals do not enter the orbit margin.

Jugal. The jugals form the majority of the cheek regions. Anteriorly, they contact the maxilla and anteromedially the lacrimal. Medially, the jugals are sutured anteriorly and in their middle part with the prefrontal and posteriorly with the postorbital. The jugal forms a narrow process and enters the orbit, thereby separating the prefrontal and the postorbital. Posteriorly, the jugals suture with the squamosal medially and the quadratojugal laterally. Pit and groove ornamentation occur in the posterior part and ridges and furrows are present in the anterior part (Figs 2, 3).

Prefrontal. The elongate prefrontals suture with the nasals and lacrimals anteromedially and anterolaterally, respectively (Figs 2, 3). Medially, towards the midline, they suture with the frontals and towards the lateral margin with the jugals and form the anterior most rim of the orbits. Ridge and furrow-like ornamentation is present on their surface.

Frontal. The frontals are conspicuous, elongate bones that are anteriorly subtriangular in shape (Figs 2, 3). They run from the middle part of the snout region to the interorbital region. Anteriorly, they are bounded by the nasals, laterally by the prefrontals, posteriomedially by the parietals, posterolaterally by the postfrontals and form a part of the rim of the orbit projecting between the prefrontals and the postorbitals. Ornamentation in the anterior part is feeble but in the posterior part pit and groove ornamentation is present.

Postfrontal. The postfrontals are pentagonal in outline and form the posteromedial margin of the orbits. Anteriorly, they suture with the frontals, posteromedially with the parietals, posteriorly with the supratemporals, and laterally with the postorbitals (Figs 2, 3). Pit and groove ornamentations is present throughout.

Postorbital. The postorbitals are wing-like projections, contributing to the posterolateral rim of the orbits (Figs 2, 3). The postorbitals contact the postfrontals medially, and the supratemporals posteromedially and project into the jugals anterolaterally. The postorbitals contact the squamosals posterolaterally. Like on the postorbitals, pit and groove ornamentation are present throughout.

Quadratojugals. The quadratojugals form the cheeks and the lateral-most part of the skull (Figs 2, 3). Dorsally, they have a sub-rectangular outline, contacting the jugals anteriorly and the squamosals medially. On the ventral side, they contact the quadrates medially. They form a larger part of the lateral and posterior rims of the subtemporal vacuities. In the occipital view, the quadratojugals suture with the quadrates medially and the squamosals dorsally. Quadratojugals have ridge and furrow ornamentation throughout.

Parietals. The parietals contact each other medially and resemble a trapezium in outline. They enclose the parietal (pineal) foramen along the medial suture towards the posterior half of the bone. The parietals suture with the frontals anteriorly, the postfrontals and the supratemporals laterally, and the postparietals posteriorly (Figs 2, 3). Pit and groove ornamentations are present throughout.

Supratemporals. The supratemporals are polygonal in outline and contact the postorbitals and postfrontals anteriorly, the parietals anteromedially, and the postparietals posteromedially. The supratemporals suture with the squamosals laterally and posteriorly with the tabulars. The supratemporal does not contribute to the rim of the otic notch (Figs 2, 3). Pit and groove ornamentation is present throughout.

Squamosals. The squamosals are located between the quadratojugals and the tabulars. They form the postero-lateral rim of the skull and almost half the anterior and lateral margin of the otic notch. The squamosals are bordered by the postorbitals and the jugals anteriorly, the supratemporals medially, and the quadratojugals laterally (Figs 2, 3). Squamosals suture with the tabulars posteromedially. Pit and groove ornamentation is present near the rim of the otic notch which gradually grades into radially oriented ridges and furrows radially at the postero-lateral corner.

Postparietals. The polygonal postparietals form the posterior concavity of the dorsal rim of the skull. The postparietals suture with the parietal anteriorly, the supratemporals anterolaterally and the tabulars laterally. They are much shorter than the parietals (Figs 2, 3). Pit and groove ornamentations are present throughout.

Tabulars. The tabulars are elongated, polygonal in shape and have posterolaterally directed horns (Figs 2, 3). The tabulars form the medial margin of the otic notch. They contact the supratemporals anteriorly, the postparietals medially, and the squamosals anterolaterally. The tabulars do not suture with the squamosal laterally thereby forming a small embayment between the tabular and the squamosal. In dorsal view, the tabular horns have a concave lateral margin. Pit and groove ornamentation is there throughout.

Lateral Line Sulci. The lateral line sulci are present as pairs of supraorbital, infraorbital, and postorbital sulci. They are more evident laterally, especially in the posterior part of the skull, and weakly impressed medially, and again pronounced across the snout. However, all the lateral line sulci are discernible. The supraorbital sulci arise from the anterior region of the snout and traverse medially to the nares. They meander anteroposteriorly from the nasals to the prefrontals, running along the prefrontal-lacrimal suture reaching the posterior half of the frontals before terminating on the postfrontals near the orbital midline (Figs 2, 3). The infraorbital sulci begin lateral to the nares and meander anteroposteriorly on the maxillae before bending acutely onto the lacrimals forming a Z-flexure and terminating atop or parallel to the jugal-maxilla sutures. The postorbital sulci originate from the postorbital rim of the orbits. They run in a sigmoid form onto the jugals and quadratojugals first, then along the squamosal-quadratojugal sutures, terminating at the posterior border of the skull.

Palate (Figs 2C, D, 3C, D).

Vomers. The vomers are elongated bones tapering posteriorly (Figs 2C, D, 3C, D). Anteriorly, the vomers suture with the premaxillae, forming the posterior margin of the anterior palatal vacuity. Immediately, behind this opening, the vomers bear a transversely arranged row of teeth. The vomers also bear palatal tusks, which are circular in cross-section. Anterolaterally, the vomers contact the maxillae and laterally contact the palatines. The vomers contribute to the medial choanal margin at the left side of the skull ISI A 54 and to most of the medial rim of the palatal vacuities. At their contact along the interpterygoid vacuities, the vomers form a V-shaped ridge that projects ventrally. The posterior part of the vomer, while bordering a considerable portion of the anteromedial borders of the interpterygoid vacuities, forms a fork-shaped extension keeping the cultriform process of the parasphenoid in between. This posterior extension is more elongate than in other mastodonsaurids. This seems to be more pronounced in ISI A 207. However, in that specimen, the palate is not well preserved. Hence, the discovery of more well-preserved specimens can only shed some light on this character state.

Palatines. The palatines are crescent in shape and bear the second pair of palatal tusks. The palatines form the posterior rim of the choanae and contact the maxillae anteriorly. The palatine-maxilla sutures run posterolaterally from the choanae to the ectopterygoid and form the anterolateral rim of the interpterygoid vacuity. The palatine has a discontinuous row of teeth more or less becoming larger anteriorly (Figs 2C, D, 3C, D).

Pterygoids. The pterygoids have a bow-like structure extending between the interpterygoid vacuities and the subtemporal vacuities and form parts of their respective rims (Figs 2C, D, 3C, D). Anterolaterally, the pterygoids contact the ectopterygoids and establish point contact with the insulae jugalis. Posteriorly, the pterygoids contact the quadrates and form part of the posterior margin of the skull. The pterygoids contact the parasphenoid medially by a serrated suture. The pterygoids do not contact the palatines. The pterygoids suture with the exoccipitals ventrally. The palatine ramus of the pterygoid bears feeble ornamentation.

Parasphenoid. The parasphenoid is an unpaired bone present in the middle of the palate (Figs 2C, D, 3C, D). The cultriform process of the parasphenoid projects beyond the anterior margin of the interpterygoid vacuities. The parasphenoid-exoccipital suture has a flat and long ‘M’ shaped outline. The crista muscularis of the parasphenoid runs transversely. Laterally, the parasphenoid sutures with the pterygoids. The parasphenoid-pterygoid sutures are as long as the width of the parasphenoid basal plate. The parasphenoid forms the posteromedial rim of the interpterygoid vacuities. The basal plate of parasphenoid is short and parasphenoid pockets are present entirely on the ventral surface of the palate. The cultriform process of the parasphenoid gradually merges with the vomers anteriorly (Figs 2C, D, 3C, D).

Ectopterygoids. The ectopterygoids are longitudinal bones. Posteromedially, the ectopterygoid sutures with the pterygoid, posteriorly with the insula jugalis, and anteriorly with the palatines (Figs 2C, D, 3C, D). The ectopterygoid bears a number of laterally compressed teeth. Ectopterygoids contribute a small portion to the rim of the interpterygoid vacuities (Figs 2C, D, 3C, D).

Insulae Jugalis. The insulae jugalis are triangular bones forming a point contact with the pterygoids posteriorly. Anteromedially, the insula jugalis is bound by the ectopterygoid and posteriorly forms a part of the anterior rim of the subtemporal vacuity (Figs 2C, D, 3C, D).

Quadrates. The quadrates are polygonal-shaped bone and contact the pterygoids medially and the quadratojugals laterally (Figs 2C, D, 3C, D). Anteriorly, the quadrates contribute to the posterior rim of the subtemporal vacuity, and posteriorly form the posterior margin of the skull. A prominent quadrate boss is present on the occipital face (Figs 2C, D, 3C, D).

Skull openings. Skull openings from the holotype ISI A 54 are listed below:

The nares are the tear-drop-shaped dorsal openings with a maximum length of 4.33 cm and maximum width 2.52 cm for the left and maximum length 4.76 cm and maximum width of 2.63 cm for the right opening. A small bone, the septomaxilla, is present at the inside of the anterolateral margin of the nares. The orbits are positioned at the posterior half of the skull with a maximum length of 5.70 cm and 5.85 cm and a maximum width of 3.76 cm and 3.30 cm respectively for left and right and they are elliptical in outline. The orbits are slightly elevated with respect to the plane of the skull roof. The pineal foramen is subcircular; its long axis is 1.68 cm and short axis is 1.03 cm, and is completely enclosed by the parietals. The otic notch is wide open posteriorly and is bounded by the squamosal and the tabular. The anterior rim of the otic notch is angular, the angles between the squamosals and the tabulars are 41 and 62 degrees in the left and right otic notch respectively. The anterior palatal vacuities are subdivided and laterally stretched with a maximum length of 2.5 cm and width of 7 cm. The left one measures 2.08 × 3.22 cm and the right one measures 1.46 × 3.49 cm. It is enclosed by the premaxillae and the vomers. The anterior palatal vacuity is bean-shaped with a constriction in between. The choanae are two slit-like cavities in the anterior part of the palate. The left and right choanae are quite deformed (taphonomically) with dimensions of 3.49 × 1.28 cm and 5.07 × 1.21 cm, respectively. The interpterygoid vacuities are the largest openings of the palate, with a ‘D’-shaped outline, they measure 28.93 × 8.08 cm and 28.91 × 9.60 cm on left and right respectively. The lateral rims have a parabolic curvature with the posterior curvature being more acute than the anterior one. The marginal rims are almost straight. The interpterygoid vacuities are enclosed by the vomers, the palatines, the pterygoids, the parasphenoid and a small portion of the ectopterygoids. The cultriform process of the parasphenoid forms most of the medial margin. The subtemporal vacuities are the posterior most vacuities in the palate. The vacuities are arch shaped with a gentle lateral convexity and a more acute medial concavity. The maximum length measured parallel to the midline is 17.30 cm, and the maximum width is 7.90 cm for the left one and 17.47 cm and 9.01 cm respectively for the right one. The subtemporal vacuities are enclosed by the pterygoids, the quadrates, the quadratojugals and the insulae jugalis. The tip of the anterior projection of the subtemporal vacuity does not reach the level of the midpoint of the interpterygoid vacuities.

Occiput (Figs 2E, F, 3E, F). The occipital process contacting postparietal and tabular is extremely short and stout dorso-ventrally in occipital view. The pterygoid oblique ridge is exceptionally short and dorsomedially oriented, located just anterior to the otic notch and approaching the crista falciformis of the squamosal. The descending ramus of the squamosal partially covers the lateral sections of the pterygoid and quadrate and extends dorsolaterally to the paraquadrate foramen at the quadrate. From its posterior corner, the quadratojugal produces a narrow but thicker flange that extends medially for a short distance along the rear surface of the quadrate. The quadrate bears a prominent quadrate boss. The post temporal fenestra is triangular in outline. The torsion in the quadrate is visible in occipital view.

Exoccipitals. The exoccipitals project posteriorly to establish the atlas-exoccipital articulation and diverge dorsally to encompass the ventral portion of the foramen magnum. They suture with the parasphenoid anteriorly. The posterior projection of the exoccipitals lies anterior to the projection of the quadrates. The posterior contact surfaces of the exoccipitals with the atlas are sub-oval in shape and are flat and narrow.

Mandible (Fig. 4). A well-preserved right mandibular ramus of Cherninia denwai (ISI A 208) was recovered from the Baki-Nala section near the village of Jhirpa, measuring almost 96 cm in length (Fig. 4). The curvature of the mandible exactly fits with the skull outline of C. denwai. Moreover, skull fragments of C. denwai are found from the same locality.

Dentary. The dentary forms the dorsal and parts of the labial and lingual surface of the anterior part of the ramus (Fig. 4). The dentary is bound ventrally by the splenials and angular in labial view; posteriorly the dentary tapers to a point and projects into the surangular. In lingual view, it is bound by the splenial and the coronoids ventrally, while it forms the anterior margin of the adductor fossa posteriorly. The dentary and the splenial are present in the anterior symphysis. The main marginal teeth are located on the dorsal surface. The symphysial region of the dentary has one large tusk.

Splenial and postsplenia l. In labial view, the splenial and postsplenial lie ventral to the dentary with the splenial located anteriorly. The region of the posterior Meckelian foramen is broken. The ventral surface is not fully preserved (Fig. 4).

Angular. The angular forms the remaining bone in the ventrolabial and some part of the ventrolingual surface (Fig. 4). It is bound by the dentary anterodorsally, by the postsplenial anteroventrally, and by the surangular dorsally in labial view. In lingual view, it is bound by the prearticular dorsally and articular posteriorly.

Surangular. The surangular forms most of the posterodorsal part of the labial surface, including that of the postglenoid area. In labial view, the surangular sutures with the angular ventrally and with the dentary anteriorly. In lingual view, it sutures with the articular posteriorly and with the angular ventrally and anteriorly with the prearticular. In dorsal view, the surangular sutures with the dentary anteriorly; lingually it sutures with the articular and forms the lingual margin of the adductor fossa (Fig. 4).

Coronoid series. The coronoid series consists of anterior, middle and posterior coronoid on the lingual surface of the mandible. They are placed ventral to the dentary and extend from shortly behind the symphysis to the leading edge of the adductor fossa. The anterior coronoid sutures with the splenial ventrally, the middle coronoid sutures with the postplenial and some part of the splenial and the posterior coronoid with the prearticular. No dentition is present in the coronoid series nor is there any process present in the coronoids (Fig. 4).

Prearticular. In lingual view, the prearticular forms the posterior half of the ramus. It sutures with the postsplenial anteriorly and dorsally with the middle and posterior coronoids. The prearticular forms the lingual margin of the adductor fossa and the lingual edge of the glenoid fossa. The prearticular does not form part of the postglenoid area and it does not suture with the splenial because it is separated by the coronoid (Fig. 4).

Articular. The articular is an endoskeletal bone that completely forms the glenoid fossa. Anterodorsally, the articular forms the posterior border of the adductor fossa. The articular is enclosed labially by the surangular and lingually by the prearticular. Ventrally, the articular is overlain by the angular. Posteriorly the articular enters the postglenoid area. The posterior extremity of the articular is not completely ossified.

Other important features of mandible (Fig. 4). The hemi-mandible is low except for its posterior area, which is dorsally straight along the posterior two-thirds and slightly curved in the anterior part. In labial view, the angular shows well-defined ornamentation that becomes less evident in the postsplenial. A highly developed mandibular sulcus is found in the back of the hemi-mandible, and the marked oral sulcus extends all the way to the dentary. There is also a tiny accessory sulcus that runs from the mandibular sulcus to the surangular. The posterior Meckelian foramen is not preserved and the anterior Meckelian foramen is absent. The adductor fossa is quite large, with an oval shape and dimensions of 21.2 cm along the long axis and 2.3 cm along the short axis. The lingual border of the articular, the labial border of the surangular, the antero-labial border of the dentary, the antero-lingual border of the posterior coronoid, and the posterior border of the glenoid fossa all encircle the adductor fossa. One anterior tusk and multiple teeth with elliptical bases can be seen in the dentary. As is characteristic in many temnospondyls, both the dentary and the splenial are a part of the symphyseal area. The articular and surangular (but not the prearticular) are located in the postglenoid region, which is considerably extended. The angular is extended to the ventral side of the articular. The foramen chorda tympani are situated more on the labial side of the post-glenoid region (dorsal). Although Jupp and Warren (1986) discussed the lower jaw anatomy of temnospondyls and stated that mastodonsaurids mostly have Type I post glenoid area, the morphology of the post– glenoid area of C. denwai cannot be clearly placed in any of the two types defined by Jupp and Warren (1986). It shares with Type I the following features: the prearticular does not extend into the postglenoid area, the articular is the major component of the postglenoid area and the angular lies ventral to the articular. On the other hand, as in Type II, the angular lies labial to the articular and the postglenoid area is slightly elongated. The prearticular hamate process is highly developed, huge, and spatulate. In comparison to the hamate process, the quadrate trochlea is shorter. There were two separate processes called the crista articularis and crista medialis. Underneath the dentary’s dorsal surface is the glenoid fossa. The elliptical, sizable adductor fossa has a horizontal and straight labial wall. The torus arcuata (muscle scar near the hamate process) is prominent and the muscle insertion area is comparatively large (Fig. 4). The shape of the glenoid fossa is rectangular. The adductor fossa’s anterior process is elevated and conspicuous.

Postcranium (Figs 5–13). All postcranial elements were retrieved from the middle part of the Denwa Formation. They are assigned to the taxon Cherninia denwai, as they were discovered either in association or in very close proximity (almost together) to the cranial fragments of the taxon. The postcranial elements were mainly collected from Purtala, Kohpani and Jhirpa villages and adjoining areas of the state of Madhya Pradesh (Central provinces), India. In Purtala and in Kohpani, they are either associated with the skull or found in close proximity, sometimes within a meter or so, in the same bed and at the same level. In Jhirpa they are associated with the mandible of C. denwai which is unique in its curvature, proportion of dentigerous area with respect to the adductor fossa and the postglenoid area. The said proportions are different from that of the brachyopids and the trematosaurid mandibles. Brachyopids and trematosaurids are the other two groups that are present in the Middle Denwa. The postcranial elements, particularly the vertebrae, of these two groups are also different from those of the mastodonsaurids (Warren and Snell 1991).

The Vertebral column. The preserved vertebral elements mainly encompass the intercentra, neural arches, and neural spines (Fig. 5). The post-atlantal and presacral neural arches are different. The presacral neural arches have less developed posterior zygapophyses with shorter neural spines than the post-atlantal arches. The neural spines of the post-atlantal vertebrae have erect spines. Most of the neural arches and neural spines were incomplete and broken in C. denwai. Atlas and axis are not present in the collection.

The intercentra are wedge-shaped in lateral view and crescentic or heart-shaped in anterior and posterior views. Distinctly, two types of intercentra are present, type 1 in the anterior part and type 2 in the posterior part. The anterior intercentra are massive, quite thick, and robust. The dorsal most part is blunt. The ventrolateral surface of the intercentrum is concave with two raised rims at the anterior and posterior borders. The parapophysis is well developed. Five anterior intercentra are preserved (ISI A 209–213). The posterior intercentra are flattened ventrally and the lateral surfaces are more distinct from the ventral face. They are shallower and less ossified than the anterior ones. The parapohyses were directed more ventrally, thus their lower edges project below the ventral line with a triangular outline. There are four posterior intercentra preserved (ISI A 214–217) (Fig. 5).

Neural arch and neural spine. Neural arch and neural spines (Fig. 6) are broken in the specimens from the middle part of the Denwa Formation. The body of the neural arch extends laterally. A rectangular facet, the area of attachment of the pleurocentrum (Watson 1958) is present. At the distal end of the transverse process, a squarish facet is present which is the diapophysis.

Neural spines were detached from the bodies of the neural arches. They are short and stout. Eight single broken neural arches (ISI A 218–225) and two broken lateral halves of a neural arch (ISI A 226a & b) are preserved. Eight neural spines have been detected (ISI A 227–234).

No haemal arches are preserved.

Ribs. A total of 30 rib fragments and one almost complete rib are present (Fig. 7). The ribs show distinct variation in morphology. The position of the ribs has been determined by the existing literature of temnospondyls ribs (Dutuit 1976; Dutuit 1978; Sengupta 2002; Sulej 2007).

The cervical ribs have two separate rib facets. The anterior thoracic rib (ISI A 235; ISI A 238–250) heads were elliptical in cross-section with a narrow extension for attachment of capitulum and tuberculum. The distal end of the anterior thoracic rib is expanded and plate-like. The posterior thoracic ribs (ISI A 251–266) are cylindrical and have elliptical proximal heads and rounded distal ends (Fig. 8). Sacral ribs are expanded both proximally and distally and are short and stout (ISI A 236–237).

No caudal ribs are preserved.

Pectoral girdle. Two almost complete and three fragmented interclavicles (ISI A 267 & 268), one complete left and one fragmented left and one fragmented right clavicle (ISI A 272–274) and six fragmented cleithra (ISI A 275–280) are present. The interclavicles are large and robust and their thickness varies from 3 to 5 cm. The clavicles have a long dorsal process originating at the posterolateral corner of the clavicular blade. The dorsal process is slender and twisted. The clavicular blades are slender and spatulate (Fig. 8).

Cleithra are slender processes having low ridges on their surfaces. A scapular crest is present at its head. The shaft’s external surface is convex. The internal facet has a concave attachment area for the clavicle and a convex attachment area for the scapula (Sulej 2007). All the cleithra are broken (Fig. 9).

Forelimb. From the forelimb, only the proximal and distal heads of the ulna are preserved in the present collection (ISI A 182/3 & 4; ISI A 281–282, Fig. 10). The specimen ISI A 182/4 was interpreted as the distal shaft of the ulna by Mukherjee et al. (2020), but the olecranon process is distinct in the specimen, so that it can be regarded as the proximal shaft of the right ulna. The proximal and distal ends of the ulna are expanded towards the radius. The proximal head is rhombohedral in outline and the posterolateral corners of the head are raised with the olecranon process. On the posterior surface, a low crest is present. The distal heads bear a laterally flattened articulation surface for ulnare and intermedium.

Pelvic girdle. The pelvic girdle comprises only the left ilium as no other elements are preserved (Fig. 11). Overall, the ilium is cylindrical with a convex ventral margin that tends to meet the puboischiadic blade (ISI A 283). A depression at the posterior part of the ilium is the area of attachment of the acetabulum head which is mostly cartilaginous. The acetabular buttress is thicker anteriorly and laterally projected. The acetabulum is bounded by two notches. The anterior supracetabular notch is slenderer and dorsally placed while the posterior acetabular notch is ventrally placed. The iliac blade is robust and cylindrical and bears some striations for attachment of muscles. The shaft is oval in cross-section.

Hind limbs. From the hindlimbs, the proximal shaft of a right femur and the proximal shaft of left fibula is preserved. The tibia is not present in the collection. The proximal shaft of the right femur (Fig. 12) shows concave anterior and posterior margins. The bone is strong and stout with a medial ridge. The adductor blade is present housing the fourth trochanter. The proximal articular surface is oval in outline (ISI A 284).

The fibula is dorsoventrally flattened, with a trapezoidal outline of the proximal head (Fig. 13). The anterior margin is concave. The well-developed posterior fibular ridge is visible, which is bordered by a furrow in the front and a raised surface made by two short parallel ridges in the back (ISI A 285).

No digit bones were found.