Geoclemys hamiltonii ( Gray, 1830 )

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 : 33-40

Geoclemys hamiltonii ( Gray, 1830)

Figs 22–26

Emys hamiltonii Gray, 1830: 9 .

Emys guttata Gray, 1832 : pl. 76.

Emys picquotii Lesson, 1831: 120 .

Emys picquotii Lesson in Duméril & Bibron, 1835: 316 .

Emys hamiltonii Duméril & Bibron, 1835: 315 .

Emys hamiltonoides Falconer & Cautley in Lydekker, 1880: 21 .

Melanochelys pictus Murray, 1884a: 107 .

Clemmys palaeindica Lydekker, 1885a: 178 .

Geoclemys sivalensis Tewari & Badam, 1969: 555 .

Geoclemys sivalensis Badam, 1979: 99 .

Clemmys (Clemmys) hamiltonii – Fitzinger 1835: 123.

Geoclemys hamiltonii – Gray 1856 (“1855”): 17.

Clemmys hamiltonii – Strauch 1862: 32.

Damonia hamiltonii – Gray 1869: 195. — Boulenger 1889: 93.

Damonia hamiltonoides – Lydekker 1880: 37.

Damonia hamiltoni – Lydekker 1889b (ex errore): 105.

Geoclemys hamoltoni – Tewari & Badam 1969 (ex errore): 1.

Type

BMNH 1947.3.4.41 ( Iverson 1992).

Material examined

INDIA • 1 specimen, holotype of Clemmys palaeindica ; Siwalik Hills ; Miocene–Pliocene; BMNH 39838 • 4 specimens; Siwalik Hills ; Miocene–Pliocene; BMNH 39840 , BMNH 39842 , BMNH R.887 ,

BMNH R.892 • 1 specimen, holotype of Geoclemys sivalensis ; Punjab, Pinjore stage , 1 km southeast of Quranwalla; Early Pleistocene; MCASG A/665 .

Type locality

“ India ” ( Iverson 1992).

Occurrence

Miocene/Pliocene – Recent.

Differential osteological diagnosis using shell characters

Geoclemys hamiltonii can be differentiated from other geoemydids by the presence of three strong longitudinal carapace keels, neurals III-VI with anterior short sides, and an entoplastron that is intersected by the humeropectoral sulcus.

Description of material examined

BMNH 39838 ( Fig. 22 ), holotype of Clemmys palaeindica – This is an almost complete, exceptionally well-preserved specimen from the Miocene/Pliocene of the Siwalik Hills, likely of India, originally figured and described by Lydekker (1885a: pl. 21.3). Our observations mostly compare with those of Lydekker, although we see more details in the plastron. The specimen appears to represent an adult due to its large size (carapace length greater than 30 cm). All sulci and sutures on the carapace and most sulci of the plastron are visible. Three longitudinal carapacial keels are present, with varying height throughout the keel. The lateral keels are closer to the neural series than to the peripheral bones. No signs of growth annuli are visible. The cervical scute is present and as long as wide. All vertebral scutes are about the same width. The first vertebral scute is longer than wide and has straight lateral margins. The second and third vertebral scutes are as long as wide. The sulcus between the second pleural and third vertebral is almost straight. Marginal scutes IV–VIII do not contact any costal bones. The eighth marginal scute is slightly serrated at the carapace margin. All neural bones are hexagonal, anteriorly short-sided, and about the same size. The second suprapygal is intersected by the sulcus between the fifth vertebral and twelfth marginal scutes. The anterior plastral margin is straight. The entoplastron is intersected by the gularohumeral sulcus anteriorly and likely by the humeropectoral sulcus posteriorly. A deep and rounded anal notch is present at the posterior plastral margin.

BMNH 39840 ( Fig. 23 ) – This is a well-preserved subadult specimen (carapace length greater than 11 cm) from the Miocene/Pliocene of the Siwalik Hills, likely of India, originally figured and described by Lydekker (1885a: pl. 1). Our observations greatly compare with those of Lydekker. The specimen is missing the posterior half of the carapace and the xiphiplastra. Almost all carapacial sulci and sutures are visible. Three longitudinal keels are present on the carapace, with discontinuous height. The median keel starts at the posterior part of vertebral I. The lateral keels start on the posterior region of costal I and are positioned closer to the neural series than to the peripheral bones. No signs of growth annuli are visible. The cervical scute is present and wider than long. The first vertebral scute is as long as wide, has straight lateral margins, and contacts the second marginal scute. The second and third vertebral scutes are about the same width and are as long as wide. The sulcus between the second pleural and the third vertebral is almost straight. All neural bones are hexagonal, anteriorly short-sided, and about the same size. Peripheral bones III–VII do not have recurved margins that would form a longitudinal gutter. The anterior plastral margin is straight, without a median notch, and has small lateral tuberosities. A small inflection on the gular scute margin is present at the edge of the gularohumeral sulcus. The entoplastron is intersected anteriorly by the gularohumeral sulcus, but not by the humeropectoral sulcus. The pectoroabdominal sulcus and hyo-hyoplastron suture do not overlap. The posterior plastral margin is not preserved.

BMNH 39842 ( Fig. 24 ) – This specimen originates from the Miocene/Pliocene of the Siwalik Hills, likely of India. It was presented to BMNH by Col. P.T. Cautley, but remains unfigured to date. It is an almost complete specimen that is missing the lateral peripheral bones and part of the anterior margin of the plastron. This is clearly an adult specimen due to large size (carapace length greater than 35 cm). The carapace surface is crushed, preventing observation of most sutures and sulci. At least the median longitudinal keel is present, crossing the first, seventh and eighth neural bones. The first vertebral scute has straight lateral margins, without any constriction, contacting the first marginal scute. The neural bones are hexagonal and anteriorly short-sided. The pygal bone is completely intersected by the intermarginal sulcus. The gular scute is longer than wide, overlapping part of entoplastron. The entoplastron is intersected posteriorly by the humeropectoral sulcus. The pectoroabdominal and abdominofemoral sulcus have two anterolateral notches, indicating the former presence of lateral longitudinal keels. The pectoroabdominal and hyo-hypoplastral suture do not overlap. The xiphiplastra have a deep anal notch. BMNH R.887 ( Fig. 25 ) – This specimen is from the Miocene/Pliocene of the Siwalik Hills, likely of India. It was presented by Col. P.T. Cautley in 1840 to BMNH, but remains unfigured until now. This is an incomplete specimen, consisting of the anterior part of the carapace and the middle part of the plastron. This is clearly an adult specimen with a total carapace length of approximately 15 cm. The nuchal, costals I–V, neural bones I–V, as well as some peripherals are preserved. A large part of the right hyo- and hypoplastron, the right bridge, and a small part of left hyo- and hypoplastron are preserved as well. A median carapacial keel and two lateral keels are clearly present. Neural bones II–V are hexagonal with anterior short sides. The first vertebral scute is longer than wide, with a small anterolateral constriction. The third vertebral has a straight lateral sulcus. The pectoroabdominal sulcus and the hyo-hypoplastral suture do not overlap. An inguinal scute is likely present.

BMNH R.892 ( Fig. 26 ) – This specimen was collected from the Miocene/Pliocene of the Siwalik Hills, likely of India, was donated to BMNH by Col. P.T. Cautley in 1840, but remained unfigured to date. Lydekker (1889b) wrongly referred to this specimen as BMNH R.829. This is an incomplete adult specimen that only consists of the plastron (plastral length greater than 25 cm). Both the anterior and posterior plastral margins are missing, as well as the right bridge and a part of the left bridge. The entoplastron is intersected by the gularohumeral sulcus anteriorly and by the humeropectoral sulcus posteriorly. The fifth marginal scute covers a part of the left bridge and overlaps onto the hyoplastron. The sixth marginal scute does not overlap the hyoplastron. The hyo-hypoplastral suture contacts peripheral V and does not overlap the pectoroabdominal sulcus. The inguinal scute is likely present.

MCASG A/665, holotype of Geoclemys sivalensis – This specimen was collected from the Early Pleistocene Pinjore stage, 1 km south-east of Quranwalla, Punjab, India. It was preliminarily figured in Tewari & Badam (1969: figs 1–2) and in Badam (1979: fig. 36A–B, pl. 27), but could not be refigured herein due to logistic constraints. The specimen consists of the anterior half portion of the carapace as well as some plastral bones. Three longitudinal carapacial keels are clearly present, the lateral ones closer to the neurals than the peripherals. Growth annuli marks are present on the pleurals and first vertebral. The first vertebral scute is longer than wide and has slight anterolateral constrictions. Neural I is oval in shape and neurals II and III are anterior short-sided. A large cervical scute is present, almost as long as wide. One hypoplastron and a bony part of the bridge are supposedly preserved, but not figured. Tewari & Badam (1969) state that mesoplastra are present, but Das (1991) indicated this to be an error.

Comments

We here attribute these specimens to Geoclemys hamiltonii based on, among other characteristics, the presence of a tricarinate carapace with interrupted median and lateral keels decorated by many prominent processes, and a cervical scute that is wider posteriorly. This confirms the synonymy of Clemmys palaeindica with G. hamiltonii , as initially suggested by both Boulenger (1889) and Lydekker (1889a), and of Geoclemys sivalensis with G. hamiltonii , as first recognized by Das (1991). These synonymies have been further supported by TEWG (2015) and TTWG (2017).

Figures

Fig. 22. BMNH 39838, holotype of Clemmys palaeindica Lydekker, 1885, here identified as synonym of Geoclemys hamiltonii (Gray, 1830). 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. 23. BMNH 39840, referred to Clemmys palaeindica Lydekker, 1885, here identified as Geoclemys hamiltonii (Gray, 1830). 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. 24. BMNH 39842, referred to Damonia hamiltonii Gray, 1869 by Lydekker (1889b), here identified as synonym of Geoclemys hamiltonii (Gray, 1830). A. Photograph of carapace. B. Illustration of carapace. C. Photograph of plastron. D. Illustration of plastron. Scale bar: 3 cm.

Fig. 25. BMNH R.887, referred to Damonia hamiltonii Gray, 1869 by Lydekker (1889b), here identified as Geoclemys hamiltonii (Gray, 1830). A. Photograph of carapace. B. Illustration of carapace. C. Photograph of plastron. D. Illustration of plastron. Scale bar: 3 cm.

Fig. 26. BMNH R.892, referred to Damonia hamiltonii Gray, 1869 by Lydekker (1889b, under the number BMNH R.829), here identified as Geoclemys hamiltonii (Gray, 1830). A. Photograph of plastron. B. Illustration of plastron. Scale bar: 3 cm.