838
Journal of Paleontology 89(5):821–844
Clarendonian of Nebraska could represent the oldest record of K. wakeeniense. Kinosternon wakeeniense was possibly contemporaneous
with Kinosternon pannekollops, but grew to a smaller adult size than K. pannekollops. Kinosternon wakeeniense is morpholo- gically similar to Kinosternon rincon (Table 1), and like K. rincon, possesses symplesiomorphies and synapomorphies with the Kinosternon flavescens and subrubrum species groups. It is similar to Kinosternon pojoaque and female members of the crown flavescens group in having a lobate plastral hindlobe that lacks a distinct anal notch, thin posterior marginal rim, and the insertion sutural pocket for C7 is situated midway on P10, a synapomorphy with K. flavescens. The hindlobe morphology of K. wakeeniense is similar to Kinosternon arizonense by a combination of shape and scute proportions. However, K. wakeeniense lacks a heightened M9 and has a narrower V1, more similar to K. rincon and the subrubrum group. Unlike K. rincon, it possesses inclined plastral bridge buttress accompanied by an inguinal groove, which it shares with the crown flavescens group and stem and crown members of the subrubrum group. Some of the type and referred specimens of Kinosternon
wakeeniense were previously reported (Holman, 1975; Bourque, 2011). None of the bones catalogued under MSU- VP 771 or MSU-VP 1177 have known associations with each other and therefore it is presumed that these specimens represent multiple individuals. As such, much of the description of this species is a composite based on isolated bones believed by the author to represent a single taxon.
Kinosternon notolophus new species Figure 8
2013 cf. Kinosternon n. sp. Bourque, pp. 470–473.
Holotype.—UF 43031, nuchal, collected by a field crew from the Florida State Museum (now the FLMNH) sometime between 1974 and 1980.
Diagnosis.—Autapomorphy: pronounced medial keel on the nuchal that is more developed than in extant kinosternines, and is broad and flattened (not sharply peaked) anteriorly along its crest (the full extent of this keel and its shape along the length of the carapace is unknown at this time; a nuchal that is keeled to a lesser degree is present in Kinosternon hirtipes murrayi [Glass and Hartweg, 1951], Kinosternon integrum, Kinosternon oaxacae, some Kinosternon scorpioides, and Kinosternon sonoriense sonoriense). Synapomorphies: Costiform processes of the nuchal short and nub-like (shared with Kinosternon pannekollops,
Kinosternon wakeeniense, Kinosternon
herrerai, K. sonoriense, and some K. scorpioides); weakly developed set of lateral carinae on costals (shared with K. h. murrayi, K. integrum, Kinosternon acutum, Kinosternon creaseri Hartweg, 1934, Kinosternon alamosae, and some K. scorpioides); posterior marginals thickened with deep visceral step (shared with K. pannekollops, the subrubrum group, Kinosternon angustipons, K. s. sonoriense, Kinosternon cruentatum, and Kinosternon leucostomum). Symplesiomorphy: nuchal contacts N1 (shared with K. pannekollops, Kinosternon
skullridgescens,K. alamosae, and the flavescens and subrubrum groups). The holotype nuchal of Kinosternon notolophus n. sp. is
distinct from extant keeled Kinosternon in possessing a more pronounced anteriorly flat-crested keel, and a combination of symplesiomorphies possessed by no single species of extant keeled Kinosternon that include: broad nuchal to N1 contact, more posteriorly situated nuchal horns, lack of an abrupt constriction posterior to the nuchal horns, relatively narrow V1 that lacks M2 contact, and broad marginal rim (comprising the M1 scute set and cervical scute) in relation to the overall width of the nuchal (Fig. 8.1). Conversely, extant keeled Kinosternon possess a nuchal with a pointed posterior pinnacle in having no N1 contact, more anteriorly situated and diminutive nuchal horns with an abrupt constriction posterior to the nuchal horns, a wider V1, and a more narrow marginal rim in relation to the maximum nuchal width. Staurotypus possesses a keeled nuchal with N1 contact, but has a much wider cervical scute and elongate costiform processes, and Sternotherus lacks a keeled nuchal and has more pronounced costiform processes.
Occurrence.—Type locality: Love Bone Bed, Alachua County, Florida. Age and formation: Late Miocene, late Clarendonian NALMA (Cl 3), 10–9 Ma, Alachua Formation (Hulbert, 2001; Tedford et al., 2004). The referred specimen UF 225682 was collected from the Suwannee River Mine, Hamilton County, Florida; Statenville Formation, early Clarendonian (Morgan, 1989; Hulbert, 2001; Bourque, 2013).
Description.—Carapace: The nuchal of Kinosternon
notolophus, UF 43031 (Fig. 8.1 and 8.2), is distinct from extant Kinosternon with a keeled nuchal in overall shape. The shape is more similar to Kinosternon pannekollops with the exception of the well-developed medial keel. There is a distinct transverse suture at the peak of the nuchal indicating broad contact with N1. V1 is narrower in K. notolophus than extant Kinosternon with a keeled nuchal and the anterior rim of the nuchal (comprised of the M1 set and cervical scute) is broader in rela- tion to the total nuchal width (Fig. 8.1). The anterior of V1 overlapped P1. The orientation of the nuchal–P1 suture (from the anterior-most point to the widest point of the nuchal) is distinct in K. notolophus compared to other keeled Kinosternon. In the former, the suture is diagonally almost straight, whereas in the latter group there is a significantly angled crook at the M1 sulcus. The nuchal lacks pronounced cervical tuberosities on the posterior-ventral side. UF 43031 possesses nub-like costiform processes
(Fig. 8.2); however, the right P1, UF 150031 (Fig. 8.4 and 8.5), exhibits a deep sutural depression on the visceral face indicating that the nuchal extended the width of P1 and probably just contacted P2. The combination of what is observed on the nuchal and that on the P1 is similar to what is observed in Kinosternon sonoriense and some Kinosternon scorpioides, where the costiform processes are not well developed but the visceral face of the nuchal extends across the visceral face of P1 and contacts P2. A pock along the dorsal M1 sulcus of UF 150031 may represent pathology at the V1 contact with M1. The proximal left C3, UF 150029 (Fig. 8.9), exhibits a lateral keel of low relief. This keel is similar to that of
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