836
Journal of Paleontology 89(5):821–844
(buttress terminates more posteriorly on P4 in K. pannekollops); pronounced lateral peripheral keel (shared with K. rincon and K. pojoaque);M10 taller thanM11 (sharedwithmost Kinosternon; in SternotherusM10 and M11 are equal in height); inguinal bridge buttress inclined with distinct inguinal groove present (shared with extant flavescens and subrubrum groups); plastral hindlobe lobate and lacks distinct caudal notch (shared with K. pojoaque and females of the flavescens group).
Occurrence.—Type locality: WaKeeney Local Fauna (Wilson, 1968; Holman, 1975). Age and formation: Late Miocene, middle–late Clarendonian NALMA (Cl 2–Cl 3), 11.5–9.5 Ma, Ogallala Formation (Wilson, 1968; Tedford et al., 2004). The referred specimen UNSM 125577 was collected from the Middle of Road Locality (USNM site WT-105), early Clarendonian component of the Ash Hollow Formation, Nebraska (G. Corner, personal communication, 2014).
Description.—Carapace: The nuchal of Kinosternon wakeeniense, MSU-VP 771 (Fig. 7.1, 7.2, and 7.7), is broad (18.45mm long and ~27.51mm wide if it were not broken) and relatively flat dorso-ventrally. Although damaged, it was much broader than long in life and compares well to Kinosternon rincon and Kinosternon steindachneri in overall shape, pro- portions, and in having narrow marginal and cervical scute margins ventrally. It lacks substantial visceral buttressing often seen in many species of Kinosternon and compares well to Kinosternon flavescens, K. rincon, Kinosternon pojoaque, and K. steindachneri in this way. The nuchal lacks a pair of pro- nounced cervical tuberosities on the posterior-ventral side. These tuberosities occur at the site where the postzygapophyses of cervical vertebra 7 articulate with the prezygapophyses of cervical vertebra 8, and are pronounced in Sternotherus and some Kinosternon such as K. herrerai, but reduced to absent in most Kinosternon. The presence or absence of pronounced cervical tuberosities could be phylogenetically informative, but was not sufficiently examined here. The suture along the posterior-most pinnacle is transverse
for 2.53mm and not sharply pointed, indicating that there was nuchal–N1 contact. The lateral sulcus of V1 did not contact M2 or overlap onto P1, but instead this sulcus terminates anteriorly on the nuchalwhere it contactsM1. The costiform process is only preserved on the right side, and is a minute nub-like structure. The nuchal MSU-VP 771 compares well with a partial
nuchal, UNSM 125577 (Fig. 7.3 and 7.4 ). UNSM 125577 was collected from a site called the Middle of Road Locality (USNM site WT-105) and is from the early Clarendonian component of the Ash Hollow Formation (= Penny Creek Local Fauna), Nebraska (George Corner, UNSM, personal communication, 2014). UNSM 125577 is ~19.02mm long and ~23.55mm wide (if it were not broken), similarly sized to the nuchal MSU-VP 771 and dorsoventrally flat in the same manner. The lateral V1 sulcus of UNSM125577 contacts onlyM1 and did not overlap onto P1. The costiform process (preserved only on the right side) is a minute nub-like structure just like that described above for nuchalMSU- VP 771. The nuchal horns of both MSU-VP 771 and UNSM 125577 are less developed than Kinosternon pannekollops,and are instead more similar to those of Kinosternon rincon.
A left P1 (part of the lot catalog number MSU-VP 1177)
(Fig. 7.5–7.7) lacks any sulcus for V1 on the dorsal surface indicating thatV1 did not overlap P1 and did not contactM2. On the ventral face, there is a very small sutural notch that would have accommodated a small nub-like costiform process that terminated in P1 and did not contact
P2.The combination of these attributes agrees with the nuchalMSU-VP 771 described above. One right and two left P4s (part of MSU-VP 1177)
(Fig. 7.8–7.13 ) all possess a distinct peripheral keel on the external surface discussed by Bourque (2012a) similar to that of Kinosternon pojoaque and Kinosternon rincon. On the visceral face, the suture for the axillary buttress is extensive and runs almost the entire length of each of the P4 specimens, and probably contacted and terminated on the posterior-most P3 as in K. rincon. A left P8 (part of MSU-VP 1177) (Fig. 7.14,7.15, and
7.22) preserves the anterior of M9. This scute is low and not as heightened as seen in Kinosternon pojoaque and the flavescens group. Also unlike these taxa, the shape of the M9 is obtusely angled and not curved on its anterior half (or wave-shaped) at its intersection with the PLR3–4 sulcus. The marginal rim is not as thick as that for Kinosternon pannekollops and the subrubrum group. Aleft P9 (part ofMSU-VP1177) (Fig. 7.16,7.17,and 7.22 )
is comparatively large (1.8 cm long and 1.6 cm high) in contrast to the rest of the kinosternid sample from the WaKeeney Local Fauna. It shows a resemblance in size, shape, and thickness to Kinosternon sonoriense and Kinosternon flavescens, although the marginal rim is slightly thicker than in K.
flavescens.The sutural pocket that accommodated the distalC7 rib end is situated approximately midway across the visceral face of the peripheral, and in this way it is most like K. flavescens. A left P10 (part ofMSU-VP 1177) (Fig. 7.18,7.19,and 7.22) is longer than tall.M10 is taller thanM11 and themarginal rimof the peripheral is thin. A pygal (part of MSU-VP 1177) (Fig. 7.20–7.22)is
from a subadult. It is small (8.84mm long, 9.32mm wide) and exhibits a subtle midline keel on V5. The keel may be ontogenetically influenced in this taxon, in that it would diminish in adults such as discussed above for Kinosternon rincon. The visceral M11 sulcus is situated approximately halfway on the pygal. An N3 (part of MSU-VP 1177) (Fig. 7.23 and 7.24) is that
of an adult and lacks any trace of a medial keel dorsally. The V2–3 sulcus is situated on the anterior third of the neural. The N3 has six sutural contacts and is posteriorly symmetrically short-sided. A left C2 and right C3 (part of MSU-VP 1177) (Fig. 7.25 and 7.26) are also smooth dorsally and lack any trace of a lateral keel. Plastron: A partial right epiplastron (part of MSU-VP
1177) (Fig. 7.27 and 7.28) is too fragmentary to discern much from. The dorsal overlap of the gular and anterior humeral scutes is preserved and relatively narrow. The left hypoplastron (part of MSU-VP 1177) (Fig. 7.29) has a highly inclined inguinal buttress and an inguinal groove. This differs from
Kinosternon rincon and Kinosternon pojoaque, which have flattened plastral buttresses and lack an inguinal groove, and Kinosternon durangoense, which has more flattened plastral bridge buttresses but possesses an inguinal groove.
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