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Journal of Paleontology 89(5):821–844
within the subrubrum group lineage (see phylogenetic results below), which today comprises some of the smallest members of Kinosternon (Iverson, 1991). A number of char- acteristics including the possession of thickly developed axillary buttresses, thick shell and posterior carapacial margin, shallow axillary notches on the hyoplastra, highly kinetic plastral lobes, and expansive plastral forelobe that could encapsulate the head and forelimbs of the turtle are shared with other species of Kinosternon (e.g., K. baurii, K. flavescens, K. leucostomum, and K. scorpioides) that are semi-terrestrial in some aspect of their life history (e.g., overland dispersal and/or subterranean aestivation). As such, these attributes could indi- cate a similar semi-terrestrial life history component for K. pannekollops. The unique arrangement of the axillary musk duct (excessively deep axillary musk duct groove and extensive anterior-most terminal foramen) could suggest this as well. Given how little is currently understood regarding how osteological features correspond to Rathke’s gland soft tissue morphology (Plummer and Trauth, 2009), one might speculate that K. pannekollops was capable of excreting copious amounts of musk through its deep canal-like musk duct grooves and likewise of producing a pungent odor. This could be advanta- geous for gender and species recognition and other intraspecific communication (Ehrenfeld and Ehrenfeld, 1973), and for long treks overland in search of new water sources, as seen in Chelydra serpentina (Linnaeus, 1758) and Kinosternon flavescens (personal observ.). Emitting plentiful secretions of aqueous musk could prove a beneficial deterrent against predators (Neill, 1948; Ehrenfeld and Ehrenfeld, 1973), and perhaps even aid in keeping the skin moist over terrestrial dispersal or during subterranean aestivation in periods of drought. These behaviors might be expected of a relatively large kinosternid inhabiting a region hypothesized as having been composed of drought-prone savanna- like floodplain habitats with peripheral temporal water bodies and numerous mammalian predators (Schultz, 1977, 1990; Pound et al., 2012). Some morphological characteristics of Kinosternon
pannekollops are similar to members of the Kinosternon scorpioides species complex. These attributes include an overall thick shell, relative large size, expansive plastron with highly kinetic fore- and hindlobes, broad plastral forelobe, shallow axillary notches on the hyoplastra, and long narrow vertebral scutes. Conceivably these similarities reflect convergence asso- ciated with more semi-terrestrial habits, in this case two separate instances in which both K. pannekollops and the K. scorpioides group exhibit modifications of the Kinosternon shell morphotype likened with that of the testudinoid box turtle morphotype. Alternatively, K. pannekollops could represent a phylogenetic intermediate between the subrubrum group and some derived species of Kinosternon with more expansive plastra, such as
Kinosternon sonoriense sonoriense, Kinosternon oaxacae, Kinosternon integrum,and the K. scorpioides complex. This scenario is not completely unfounded when considering that Kinosternon notolophus (described below), interpreted here as a close relative of K. pannekollops and the subrubrum group (see Discussion), shares some morphological similarities with K. s. sonoriense and K. scorpioides, such as a tricarinate carapace and nub-like costiform processes.
Kinosternon wakeeniense new species Figure 7
1968 Kinosternon Wilson, p. 96. 1975 Sternotherus odoratus Holman, p. 57, fig. 2. 1981 Sternotherus odoratus Holman, p. 256.
2011 cf. Kinosternon sp. and Kinosternon sp., Bourque, p. 235, fig. 1.
2012a Kinosternon sp. cf. aff. flavescens and subrubrum Bourque, p. 78, fig. 9.
Holotype.—MSU-VP 771, nuchal.
Diagnosis.—Symplesiomorphies: nuchal with broad N1 contact (shared with some Kinosternon; extant Sternotherus lacks N1 contact); V1 narrow and lacks contact with M2 (shared with Kinosternon pannekollops, Kinosternon herrerai, Kinosternon skullridgescens, Kinosternon rincon,and Kinosternon notolophus); M9 as tall as M8 (shared with most Kinosternon excluding Kinosternon pojoaque and the flavescens group); M8–10 thin and flared and lack deep visceral step (Kinosternon angustipons, K. pannekollops, and the subrubrum group have thick M8–10 with a deep visceral step and non-flared posterior marginals); femoral scute long at the midline (shared with K. pannekollops; K. rincon; Kinosternon arizonense, Kinosternon sonoriense longifemorale, K. angustipons; K. herrerai, and K. skullridgescens) and overlaps ~40% of the hindlobe (shared with K. rincon and K. arizonense). Synapo- morphies: Lateral sulci of V1 do not extend onto P1 (shared with K.
rincon, extant Sternotherus, some Kinosternon
steindachneri, and aberrant individuals of the subrubrum group); costiform processes diminutive and nub-like, only contacting P1 viscerally (shared with K. pannekollops; Sternotherus has more elongate costiform processes); nuchal horns (Appendix 1: ch. 5) reduced but present (shared with K. rincon); overall nuchal width relatively broad (the nuchal of Sternotherus is comparatively more narrow); carapace acarinate (possibly with slight medial keel posteriorly in young indivi- duals); axillary bridge buttress extends across entire visceral P4 (sharedwithK. rincon) probably terminating at posterior-most P3
Figure 7. Type and referred specimens of Kinosternon wakeeniense n. sp. (1, 2) holotype, MSU-VP 771, nuchal in (1) dorsal; and (2) ventral aspects. (3, 4)cf. K. wakeeniense, UNSM125577, nuchal in (3) dorsal; and (4) ventral aspects. (5, 6) MSU-VP 1177, left P1 in (5) ventral; and (6) dorsal aspects. (7) Reconstruction of anterior carapace in dorsal aspect. (8, 9) MSU-VP 1177, left P4 in (8) ventral; and (9) dorsal aspects. (10, 11) MSU-VP 1177, left P4 in (10) ventral; and (11) dorsal aspects. (12, 13) MSU-VP 1177, right P4 in (12) dorsal; and (13) ventral aspects. (14, 15) MSU-VP 1177, left P8 in (14) dorsal; and (15) ventral aspects. (16, 17) MSU-VP 1177, right P9 in (16) dorsal; and (17) ventral aspects. (18, 19) MSU-VP 1177, left P9 in (18) dorsal; and (19) ventral aspects. (20, 21) MSU-VP 1177, pygal in (20) dorsal; and (21) ventral aspects. (22) Reconstruction of external posterior carapace. (23, 24) MSU-VP 1177, N3 in (23) dorsal; and (24) ventral aspects. (25) MSU-VP 1177, proximal left C2 in dorsal aspect. (26) MSU-VP 1177, right C3 in dorsal aspect. (27, 28) MSU-VP 1177, partial right epiplastron in (27) ventral; and (28) dorsal aspects. (29) MSU-VP 1177, left hypoplastron in ventral aspect. (30, 31) MSU-VP 771, right xiphiplastron in (30) ventral; and (31) dorsal aspects. Scale bar equals 1cm. Abbreviations: C7, insertion point for the distal C7 rib end; cp, costiform process; cps, insertion point of the costiform process;M8–M11, marginal scutes 8–11; mk, medial keel; N1s, neural 1 sutural contact; P8–P10, peripherals 8–10; pyg, pygal; V1, vertebral scute 1.
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