Palatochelydia

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 : 8-13

Palatochelydia sensu Joyce & Lyson, 2010

Figs 4–9

Differential osteological diagnosis

Palatochelydians can be diagnosed by the presence of a well-developed secondary palate ( Joyce & Lyson 2010), as well as the presence of a well-developed bridge, strong axillary and inguinal buttress, the latter in clear contact with both the fifth and sixth costals, anteriorly short sided second to sixth neural bones, and the universal presence of a triangular or rounded anal notch ( Garbin et al. 2018).

Material examined

INDIA • 3 specimens; Siwalik Hills ; Miocene–Pliocene; BMNH R.329 , BMNH R.959 , BMNH 16204 • 2 specimens; Piram Island , Gulf of Cambay, Gujarat; late Miocene–Pliocene; BMNH R.603 , BMNH R.958 .

PAKISTAN • 1 specimen; Punjab, Hassnot ; Miocene–Pliocene; IM E.94 .

Description BMNH R.329 ( Fig. 4 ) – This is an incomplete specimen from the Miocene–Pliocene Siwalik Hills, likely of India, that was transferred to BMNH from the Indian Museum in 1880 ( Lydekker 1889b). It was originally referred to Damonia hamiltoni (Gray 1831) by Lydekker (1889b), but remained unfigured. It consists of an articulated right lateral portion of a carapace formed by right peripherals III–VI, right costal I, and a part of the hyo- and hypoplastron ( Fig. 4 ). All sutures and almost all sulci are visible. Growth annuli marks are preserved over costal I and peripherals IV–VI. Marginal V and VI overlap a portion of the hyoplastron, the second only covering a small portion of it. An inguinal scute likely present.

BMNH R.603 ( Fig. 5 ) – This is an incomplete specimen from the Late Miocene–Pliocene of Piram Island, Gulf of Cambay, Gujarat, India that was presented to BMNH by Diwan Wajeshanker Gowreeshanker in 1885 and that was originally referred to Hardella thurgi (Gray, 1831) by Lydekker (1889b). No figure

was associated. It consists of the right side of the carapace, with preserves parts of neurals I–IV, right costals I–VI and some right lateral peripherals, which are not clearly identifiable. It is clearly an adult specimen due to its large size and probably a male specimen due to the presence of two fontanelles adjacent to right costal III. Growth annuli marks are preserved on costals I, III and V. Neurals II–IV are likely hexagonal, with short sides faced anteriorly. The carapace is smooth and lacks signs of keels.

BMNH R.958 ( Fig. 6 ) – This is an incomplete specimen from the Late Miocene–Pliocene of Piram Island, Gulf of Cambay, Gujarat, India that was transferred to BMNH from the East Indian Company Museum in 1880. Lydekker (1889b) originally referred this specimen to Hardella thurgi , but wrongly under the catalog number BMNH R.954. No figure was associated. Almost all sutures are obscured and this specimen therefore likely represents an adult, with a highly fused carapace. The only evident bones are right costals I–III, right peripherals IV–VI, and the right hyo- and hypoplastron. No signs of carapacial keels or growth annuli marks are present. Three fontanelles are apparent, adjacent to costal bones II and III, that suggesting that it is probable a male specimen. A strong axillary buttress is present. The hyo-hypoplastral suture contacts peripheral V, and an inguinal scute is present, over the right hypoplastron.

BMNH R.959 ( Fig. 7 ) – This specimen from the Pliocene of the Siwalik Hills, likely of India, was presented to BMNH by P.T. Cautley in 1840. It was referred to Hardella thurgi by Lydekker (1889b), but without a figure. This is an almost complete specimen and clearly an adult (plastron length about 52 cm). The plastron is well preserved, but the carapace lacks visible sutures. Both the anterior and posterior plastral margins are missing, as well as the posterior peripheral bones. The entoplastron is large, intersected anteriorly by the gularohumeral sulcus, but not by the humeropectoral sulcus. The anterior portion of the entoplastron is larger than the posterior portion, at least as marked by the epi-hyoplastral

suture. The hyo-hypoplastral suture contacts peripheral V and does not overlap the pectoroabdominal sulcus. The fifth marginal scute overlaps part of the hyoplastron.

BMNH 16204 ( Fig. 8 ) – This specimen originates from the Pliocene of the Siwalik Hills, likely of India, and was presented to the BMNH by P.T. Cautley in 1840. It was originally referred to Hardella thurgi (Gray, 1831) by Lydekker (1889b), but not accompanied by a figure. This is an incomplete specimen consisting of the anterior half of a shell. The plastron is well preserved, but the carapace is crushed in the center. No carapacial keels, growth annuli, or intercostal fontanelles are preserved or present. The right lateral margin of the first vertebral scute is straight, suggesting the presence of square-shaped vertebrals. Both the anterior and posterior plastral margins are missing, as well as the posterior peripheral bones and posterior half of the plastron. The entoplastron is not preserved, but the posterior position of the humeropectoral sulcus suggests that it was not intersected by it. The hyo-hypoplastral suture does not overlap the pectoroabdominal sulcus and contacts peripheral V. The fifth marginal scute forms the bridge and overlaps part of the hyoplastron.

IM E.94 ( Fig. 9 ) – This specimen from the Miocene–Pliocene of Hassnot, Punjab, Pakistan ( Lydekker 1885a) consists of the central portion of a carapace that clearly documents all sutures and some sulci. It

was originally figured and referred to Batagur falconeri Lydekker, 1885 by Lydekker (1885a: pl. 25.1). The first to fourth neurals are present and show anterior short-sides. A small midline knob can be seen on neural IV. Growth annuli marks are visible on the right anterior peripherals and on costals I, II and IV.

Comments

The six specimens herein referred to Palatochelydia indet. were initially either referred to the extinct Batagur falconeri or the extant Damonia hamiltoni (i.e., Geoclemys hamiltonii ) and Hardella thurgi (i.e., Hardella thurjii ) ( Lydekker 1885a, 1889b), though not always with high confidence (see Lydekker 1889b for BMNH 16204). Although all historical attributions are consistent with the available data, the referred specimens lack diagnostic osteological characters that positively confirm these or any other species-level identifications. Thus, we here refer these specimens to ‘Palatochelydia’ indet., due to the presence of a well-developed bridge and large size. See Discussion (Indeterminate specimens) for more details.

Figures

Fig. 4. BMNH R.329, referred to Damonia hamiltoni (Gray, 1830) by Lydekker (1889b), here identified as Palatochelydia indet. A. Photograph of carapace in lateral view. B. Illustration of carapace in lateral view. Scale bar: 3 cm.

Fig. 5. BMNH R.603, referred to Hardella thurgi (Gray, 1831) by Lydekker (1889b), here identified as Palatochelydia indet. A. Photograph of right carapace side. B. Illustration of right carapace side. Scale bar: 3 cm.

Fig. 6. BMNH R.958, referred to Hardella thurgi (Gray, 1831) by Lydekker (1889b, under the number BMNH R.954), here identified as Palatochelydia indet. 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. 7. BMNH R.959, referred to Hardella thurgi (Gray, 1831) by Lydekker (1889b), here identified as Palatochelydia indet. A. Photograph of plastron. B. Illustration of plastron. Scale bar: 3 cm.

Fig. 8. BMNH 16204, referred to Hardella thurgi (Gray, 1831) by Lydekker (1889b), here identified as Palatochelydia indet. A. Photograph of carapace. B. Illustration of carapace. C. Photograph of plastron. D. Illustration of plastron. Scale bar: 3 cm.

Fig. 9. IM E.94, referred to Batagur falconeri Lydekker, 1885, here identified as Palatochelydia indet. A. Photograph of carapace. B. Illustration of carapace. Scale bar: 3 cm.