828
Journal of Paleontology 89(5):821–844
Etymology.—Named for the Rincon Quarry, Rincon Fork of Canyada de Zia, and the nearby Rincon Fault which are all situated in the type area of the species. The word ‘rincón’ is Spanish for ‘corner.’
Referred material.—FAM 13014, peripherals and fragments of a partial shell.
Remarks.—Kinosternon rincon is morphologically similar to Kinosternon pojoaque. These two species also overlap tempo- rally and the type locality of each is in north central New Mexico, K. rincon from the Cerro Conejo Formation of the northern Albuquerque Basin and K. pojoaque from the Pojoa- que Member of the Tesuque Formation in the central Española Basin (Bourque, 2012a). The mammalian faunas associated with the Cerro Conejo Formation and Pojoaque Member are very similar (Tedford, 1981; Morgan and Lucas, 2001; Tedford et al., 2004). As such, it is conceivable that K. rincon and K. pojoaque are synonymous, with their most significant dif- ferences attributable to either a high degree of character varia- bility and/or sexual dimorphism between male and female K. pojoaque (which only a more robust fossil sample will elu- cidate). However, the holotype of K. rincon is differentiated from the types of K. pojoaque in a number of traits that include the following (see also Table 1): narrow V1 width to carapace length (V1 is wider in K. pojoaque); V1 without overlap onto P1 and contacts M1 only (V1 overlaps P1 in the types of K. pojoaque and contacts M1–2); four posteriorly symmetrical neurals (K. pojoaque has five); M11 lower than M10 (M11 is about as high as M11 in K. pojoaque); more pronounced anal notch (the holotype of K. pojoaque lacks an anal notch, but the paratype possesses a minimal notch);M5–6 sulcus contacts the inguinal scute on the hyoplastron (contacts the axillary scute on the hyoplastron in K. pojoaque); lacks conspicuous indications of medial plastral scute skin (plastral scute skin is present in at least the paratype of K. pojoaque); long intergular scute (the holotype of K. pojoaque possesses a short intergular while the paratype possesses a long intergular); longer femoral scute overlap on the plastral hindlobe; short anal scute (the types of K. pojoaque possess a short to intermediate anal); more anterior- posteriorly narrow hyoplastron with less deep axillary notches (the hyoplastron is longer in relation to width and axillary notches deeper in K. pojoaque); an axillary buttress that extends into the posterior of P3 (terminates on anteriormost P5 or pos- teriormost P4 in K. pojoaque); costiform process that terminates in P2 (terminates at the P1–2 suture in K. pojoaque); M9 that is only moderately heightened and differently shaped (more similar to Kinosternon integrum and the Kinosternon scorpioides complex in a combination of characteristics than to K. pojoaque, which has a taller M9 that is curved at its anterior). The partial shell of a Kinosternon (NMMNH 63853) was
previously reported from the Pojoaque Member of Rio Arriba County, New Mexico (Bourque, 2012b). This specimen differs from the types of Kinosternon pojoaque and Kinosternon rincon. NMMNH 63853 looks more like K. pojoaque in possessing a much wider V1 than K. rincon as well as an axillary buttress that terminates more posteriorly than in K. rincon, but it lacks a heightened wave-shaped M9 unlike the types of K. pojoaque and more like K. rincon.
Table 1. Comparison of middle to late Miocene Kinosternon Characteristic
Distribution NALMA Formation
Carapace carination M9 height
V1 to P1 overlap
Kinosternon skullridgescens New Mexico
Barstovian Tesuque
acarinate
not heightened (same as M8; shorter than M10)
V1 overlaps P1
V1 to marginal contact V1 contacts M1 only Costiform process Neural count
Femoral to hindlobe overlap overlap <40% of hindlobe Caudal notch
Axillary buttress terminus Posterior marginal rim
Inguinal buttress of hypoplastron
thin, flared present
slight inguinal groove; buttress slightly inclined
posterior-most P3 to anterior-most P4
moderate, contacts P2 6 neurals
Kinosternon pojoaque Kinosternon rincon New Mexico
Barstovian Tesuque
acarinate
heightened (taller than M8; as tall as M10), wave-shaped
V1 overlaps P1
Cerro Conejo acarinate
New Mexico Barstovian
moderately heightened, not wave-shaped
V1 contacts M1 and M2 V1 contacts M1 only moderate, contacts P2 moderate, contacts P2 5 neurals
5 neurals
overlap <40% of hindlobe overlap ≥40% of hindlobe overlap ≥40% of hindlobe absent (females only?) present
thin, flared thin, flared thin, flared absent (females only?)
lacks inguinal groove; buttress flat
lacks inguinal groove; buttress flat
inguinal groove; inguinal buttress inclined
posterior-most P4 to anterior-most P5
posterior-most P3 to anterior-most P4
Kinosternon wakeeniense Kansas, Nebraska
Ogallala, Ash Hollow (?) Clarendonian
acarinate (or slight posterior- medially)
not heightened (same as M8; shorter than M10)
V1 does not overlap P1 V1 does not overlap P1 V1 contacts M1 only
nub-like, contacts P1 N/A
posterior-most P3 to anterior-most P4
Kinosternon pannekollops Texas
Clarendonian Ogallala
acarinate
not heightened (same as M8; shorter than M10)
V1 overlaps P1
V1 contacts M1 only nub-like, contacts P1 5 neurals
middle P4
overlap <40% of hindlobe present
thick, not flared
inguinal groove; inguinal buttress inclined
Kinosternon notolophus
Florida
tricarinate N/A
Alachua, Statenville (?)
Clarendonian
V1 overlaps P1
V1 contacts M1 only
N/A N/A
nub-like, barely contacts P2
thick N/A N/A N/A
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