Melanochelys sivalensis ( Theobald, 1877 ) Garbin & Bandyopadhyay & Joyce, 2020

Garbin, Rafaella C., Bandyopadhyay, Saswati & Joyce, Walter G., 2020, A taxonomic revision of geoemydid turtles from Siwalik-age of India and Pakistan, European Journal of Taxonomy 652, pp. 1-67 : 40-47

Melanochelys sivalensis ( Theobald, 1877) comb. nov.

Figs 27–31

Bellia sivalensis Theobald, 1877: 44 .

Clemmys hydaspica Lydekker, 1885a: 172 .

Clemmys theobaldi Lydekker, 1885a: 173 .

Clemmys punjabiensis Lydekker, 1885a: 175 .

Geoemyda trijuga Smith, 1931: 97 (part).

Geoemyda sivalensis Smith, 1931: 89 .

Melanochelys trijuga indopeninsularis TEWG, 2015: e.46.

Bellia theobaldi – Lydekker 1889a: 58.

Clemmys sivalensis – Lydekker 1885a: 171.

Bellia sivalensis – Lydekker 1889a: 58.

Type

IM E.88, the anterior half of a fossil shell ( Fig. 27 ).

Material examined

PAKISTAN • 1 specimen, holotype of Bellia sivalensis ; Punjab, south of Jhand ; Middle to Upper Siwalik group of Potwar Plateau; Miocene–Pliocene; IM E.88 • 1 specimen, holotype of Clemmys theobaldi ; Punjab, Jhand; Middle to Upper Siwalik group of Potwar Plateau; Miocene–Pliocene; IM E.89 • 1 specimen; Punjab, Potwar Plateau ; Middle to Upper Siwalik group of Potwar Plateau; Miocene– Pliocene; IM E.90 • 1 specimen, holotype of Clemmys punjabiensis ; Punjab; Middle to Upper Siwalik group of Potwar Plateau; Miocene–Pliocene; IM E.92 • 1 specimen, holotype of Clemmys hydaspica ; Punjab, Jhelum district; Middle to Upper Siwalik group of Potwar Plateau; Miocene–Pliocene; IM E.93 .

Type locality and horizon

Miocene/Pliocene, Middle to Upper Siwaliks of Potwar Plateau, south of Jhand, Punjab, Pakistan (see Comments below).

Range

Miocene/Pliocene, Middle to Upper Siwaliks of Potwar Plateau, Punjab, Pakistan.

Differential osteological diagnosis using shell characters

Melanochelys sivalensis can be differentiated from other species of Melanochelys by the lack of longitudinal carapacial keels, the presence of hexagonal second to fourth vertebral scutes with concave posterolateral margins that are broader than long and a denser and more rounded shell.

Description of material examined

IM E.88 ( Fig. 27 ), holotype of Bellia sivalensis – This is the anterior half of a shell from the Miocene/ Pliocene, Middle to Upper Siwaliks of Potwar Plateau, south of Jhand, Punjab, Pakistan (see Comments below), initially figured and described by Lydekker (1885a: pl. 20.1). Our observations of the specimen mostly agree with those of Lydekker, although we document more details in the plastron. Most scutes are clearly visible, but only a few bony sutures are apparent. There are no signs of carapacial keels, but notches on the intervertebral sulci indicate the former presence of keels as a juvenile. This is clearly an adult specimen due to its large size (carapace length greater than 20 cm). Growth annuli marks are present on the anterior marginal scutes. The cervical scute is extremely reduced and clasped between the first marginals. First vertebral scute is longer than wide. The second and third vertebrals have rounded lateral margins. The plastron not well preserved, with few visible sutures. The anterior margin of the plastron is straight and the gular scutes are much longer than wide.

IM E.89 ( Fig. 28 ), holotype of Clemmys theobaldi – This is the anterior half of a shell from the Miocene/ Pliocene, Middle to Upper Siwaliks of Potwar Plateau, Jhand, Punjab, Pakistan (see Comments below) originally figured by Lydekker (1885a: pl. 20.2). Our illustrations mostly agree with those of Lydekker, but we disagree in the presence of a cervical and document the plastron for the first time. Most scutes are clearly visible, but only a few bones are apparent. It is clearly an adult specimen due to its large size (carapace length greater than 20 cm). There are no signs of carapacial keels or growth annuli marks. The cervical scute is present and as long as wide. The first vertebral scute is wider than long and exhibits an anterolateral constriction. The second and third vertebrals have rounded lateral margins. The anterior margin of the plastron is straight and lacks a median notch. The gular scutes are much longer than wide and completely intersect the entoplastron. The humeropectoral sulcus completely crosses the entoplastron posteriorly. The pectoro-abdominal sulcus does not intersect the hyo-hypoplastral suture.

IM E.90 ( Fig. 29 ) – This is a nearly complete, previously unfigured shell from the Miocene/Pliocene, Middle to Upper Siwaliks of Potwar Plateau, Punjab, Pakistan. Old ontogenetic age combined with poor preservation of the surface makes it near impossible to discern most scutes and sutures. There are no signs of carapacial keels or growth annuli marks. The cervical scute is extremely reduced and placed between the first marginals. The gular scutes are much longer than wide.

IM E.92 ( Fig. 30 ), holotype of Clemmys punjabiensis – This specimen was collected from the Miocene/ Pliocene, Middle to Upper Siwaliks of Potwar Plateau, Punjab, Pakistan, and was initially figured and described by Lydekker (1885a: pl. 20.3). Our observations of this specimen overall confirm those of Lydekker, although we document some addition sutures. The specimen represents the anterior half of a carapace and articulated fragments of the plastron, and likely represents an adult specimen due to its larger size (carapace length greater than 15 cm). Scutes are clearly discernable, but sutures are restricted to the periphery of the specimen. No carapacial keels or growth annuli marks are visible. The first vertebral scute is as long as wide and has an anterolateral constriction. The second and third vertebral scutes have semi-sinuous lateral margins. The anterior plastral margin is concave. The gular scute is longer than wide. The pectoro-abdominal sulcus does not intersect the hyo-hyoplastral suture.

IM E.93 ( Fig. 31 ), holotype of Clemmys hydaspica – This specimen consists of a nearly complete carapace and an articulated partial plastron from the Miocene/Pliocene, Middle to Upper Siwaliks of Potwar Plateau, Jhelum district, Punjab, Pakistan. The figures provided by Lydekker (1885a: pl. 20.4) overall agree with our figure, although we see more details in some areas, but less in others. This is a well-preserved specimen that clearly documents most sulci, but only some sutures. It is likely an adult specimen due to its large size (carapace length greater than 15 cm). The plastron is highly damaged and provides no information and we therefore do not figure it. There are no signs of carapacial keels or growth annuli marks. The first vertebral scute is wider than long and has straight lateral margins. The second and third vertebral scute have convex anterolateral and concave posterolateral sides. The sulcus between the first and second pleural, and the second and third pleural contact the fourth and sixth marginal scutes, respectively. The first neural bone only contacts the second costal on the right side, which is probably an anomaly.

Comments

Two of five specimens listed in this section originate from “south of Jhand” ( Lydekker 1885a). We were able to locate three places called J(h)and in the Punjab of Pakistan and India: the large town of J(h)and in Attock District, Pakistan, the village of J(h)and in Chakwal District, Pakistan and the village of J(h) and in Jalandhar District, India. The two locations in Pakistan are surrounded by sedimentary exposures that have yielded fossils of Siwaliks age, while the Indian location is located in a flood plain lacking such exposures. We therefore are highly confident that the type locality is positioned in the Punjab of Pakistan. See Discussion for further details regarding the referral of this material to Melanochelys sivalensis .

Figures

Fig. 27. IM E.88, holotype of Bellia sivalensis Theobald, 1877, here identified as Melanochelys sivalensis (Theobald, 1877) comb. nov. A. Photograph of carapace. B. Illustration of carapace. C. Photograph of carapace in lateral view. D. Illustration of carapace in lateral view. E. Photograph of plastron. F. Illustration of plastron. Scale bar: 3 cm.

Fig. 28. IM E.89, holotype of Clemmys theobaldi Lydekker, 1885, here identified as Melanochelys sivalensis (Theobald, 1877) comb. nov. A. Photograph of carapace. B. Illustration of carapace. C. Photograph of carapace in lateral view. D. Illustration of carapace in lateral view. E. Photograph of plastron. F. Illustration of plastron. Scale bar: 3 cm.

Fig. 29. IM E.90, referred to Clemmys sivalensis (Theobald, 1877) by Lydekker (1885a), here identified Melanochelys sivalensis (Theobald, 1877) comb. nov. A. Photograph of carapace. B. Illustration of carapace. C. Photograph of plastron. D. Illustration of plastron. Scale bar: 3 cm.

Fig. 30. IM E.92, holotype of Clemmys punjabiensis Lydekker, 1885, here identified Melanochelys sivalensis (Theobald, 1877) comb. nov. A. Photograph of carapace. B. Illustration of carapace. C. Photograph of carapace in lateral view. D. Illustration of carapace in lateral view. E. Photograph of plastron. F. Illustration of plastron. Scale bar: 3 cm.

Fig. 31. IM E.93, holotype of Clemmys hydaspica Lydekker, 1885, here identified as Melanochelys sivalensis (Theobald, 1877) comb. nov. A. Photograph of carapace. B. Illustration of carapace. C. Photograph of carapace in lateral view. D. Illustration of carapace in lateral view. Scale bar: 3 cm.