Kinkonychelys rogersi, Gaffney & Krause & Zalmout, 2009

Gaffney, Eugene S., Krause, David W. & Zalmout, Iyad S., 2009, Kinkonychelys, A New Side-Necked Turtle (Pelomedusoides: Bothremydidae) from the Late Cretaceous of Madagascar, American Museum Novitates 3662, pp. 1-28 : 4-15

Kinkonychelys rogersi , new species

TYPE SPECIMEN: UA 9748, a nearly complete skull, including the basicranium, but missing the premaxilla, vomer, squamosal, and quadratojugal (figs. 2–4, 8; table 2).

TYPE LOCALITY: MAD 07-25 (latitude 16 ° 7 9 14.5 0 S, longitude 45 ° 44 9 10.7 0 E) in the Lac Kinkony Study Area (fig. 1). MAD 07-25 lies approximately 2 km north of the western end of Lac Kinkony and 4.9 km northeast of the village of Antongomena .

HORIZON: Unnamed member, Maevarano Formation, Maastrichtian, Upper Cretaceous. UA 9748 was excavated in situ from facies that represent a new and soon to be described member of the Maevarano Formation that crops out above typical exposures of the Masorobe and Anembalemba Members. This new unit, which yields abundant, well-preserved fossils of aquatic taxa (ray-finned fishes, turtles, crocodyliforms) and nonavian dinosaurs, is exposed in an outcrop belt that extends along the northwest shore of Lac Kinkony and continues westward for several km toward the town of Soalala. The turtle skull was collected from the upper few centimeters of a bed of gray silty claystone intercalated immediately beneath a bed of white calcareous sandstone that shows evidence of tidal influence. In a regional sense, the stratigraphy of this new unit indicates that it likely correlates with the Miadana Member, and thus is somewhat younger than the wellknown exposures of the Anembalemba Member in the Berivotra Study Area to the west ( Rogers et al., 2000).

DIAGNOSIS: As for genus.

ETYMOLOGY: Named for Raymond R. Rogers, discoverer of the type specimen, in recognition of his important discovery but also of his many contributions to knowledge of the stratigraphy, sedimentology, and taphonomy of Upper Cretaceous strata of the Mahajanga Basin .

REFERRED MATERIAL: The following specimens, all recovered from the Anembalemba Member of the Maevarano Formation in the Berivotra Study Area, are also assigned to Kinkonychelys rogersi: FMNH PR 2650 , left maxilla with partial jugal and palatine from locality MAD 05-04; FMNH PR 2651, partial left maxilla from locality MAD 96-03; FMNH PR 2652, partial left maxilla from MAD 99- 31; FMNH PR 2653, right ramus of lower jaw, lacking articulation, from locality MAD 99-31; UA 8652, left maxilla from locality MAD 93-18; and UA 8655, partial right maxilla and jugal from locality MAD 93-18.

DESCRIPTION

Figures 2–4 , 8

PREFRONTAL

PRESERVATION: Both prefrontals are present in UA 9748 but are cracked through their ventral processes, although most of the processes are preserved attached to the maxillae.

CONTACTS: As in other Kurmademydini , the contacts of the prefrontal in UA 9748 are with the other prefrontal on the midline, the maxilla anteroventrolaterally, and the frontal posteriorly.

STRUCTURES: The dorsal margin of apertura narium externa in UA 9748 is slightly protruding as in Kurmademys, ISI R 159 ( Gaffney et al., 2006: fig. 61). The dorsal margin of the orbit and the interorbital distance in Kinkonychelys is also similar to that in Kurmademys . The sulcus olfactorius is preserved on the ventral surface of the prefrontal in UA 9748; it and the roof of the fossa nasalis are slightly wider than in Kurmademys . The anteroventral process of the prefrontal forms the edge of foramen orbitonasale, as in other pleurodires.

FRONTAL

PRESERVATION: Both frontals are present in UA 9748 but have broken margins along some of their lateral surfaces. The dorsal contacts are clear but some of the ventral edges are missing posteriorly.

CONTACTS: As in other Kurmademydini , the contacts of the frontal in Kinkonychelys are with the other frontal on the midline, the prefrontal anteriorly, the postorbital posterolaterally, and the parietal posteriorly.

STRUCTURES: Although the anterolateral margin of the frontal is broken away on both sides, it is very likely that it entered the orbital margin. On its ventral surface the frontal shows the sulcus olfactorius, which is slightly wider in Kinkonychelys than it is in Kurmademys .

PARIETAL

PRESERVATION: Both parietals are present in UA 9748 but have much of their edges broken. The dorsal plate lacks its lateral edges for most of its length. There is a natural margin along the more posterior edge of the right parietal and this indicates a deep emargination (see below).

CONTACTS OF DORSAL PLATE: As in Kurmademys , the contacts of the parietal dorsal plate in UA 9748 are with the other parietal on the midline, the frontal anteriorly, and the postorbital laterally.

STRUCTURES OF DORSAL PLATE: The extent of the temporal emargination in UA 9748 is poorly preserved, but a small natural edge on the right parietal shows that there was an extensive emargination, similar to or the same as in other Kurmademydini .

The ventral process lateral to the sulcus palatinopterygoideus is represented in UA 9748 only by the base, and its extent and contacts are not determinable.

CONTACTS OF PROCESSUS INFERIOR PARIE- TALIS: In UA 9748 the processus is broken away along its base on both sides, but most of the ventral contacts are visible as fragments on the crista pterygoidea. The processus contacts the pterygoid ventrally, the prootic posteroventrally, and the supraoccipital posteriorly. The anteroventral contact with the palatine seen in Kurmademys is not determinable in UA 9748.

STRUCTURES OF PROCESSUS INFERIOR PARIE- TALIS: The foramen nervi trigemini in UA 9748 is bordered by the parietal anterodorsally, the prootic dorsolaterally, and the pterygoid ventrally, as in other bothremydids.

JUGAL

PRESERVATION: Both jugals are present, but neither is complete and both lack their posterior areas and most of the internal contacts.

CONTACTS OF LATERAL PLATE: The jugal in UA 9748 contacts the maxilla anteroventrally and the postorbital dorsally. Possible quadratojugal and quadrate contacts are indeterminate.

STRUCTURES OF LATERAL PLATE: The jugal in Kinkonychelys forms the posterior part of the orbital margin, as in the other Kurmademydini , but it has a greater orbital exposure than in the other taxa. Although the posterodorsal part of the jugal is missing in UA 9748, the posteroventral part is intact on both sides and shows the cheek margin. There is clearly a jugal exposure along the cheek, in contrast to Kurmademys , and the degree of cheek emargination, while not determinable posteriorly in UA 9748, is higher, anteriorly at least, in Kinkonychelys than in Kurmademys and probably in Sankuchemys .

CONTACTS OF MEDIAL PROCESS: In the floor of the orbit (dorsal view), the jugal in UA 9748 contacts the maxilla anteriorly and laterally and the palatine medially, in a suture pattern very similar to that in Kurmademys . In the septum orbitotemporale (i.e., the postorbital wall) the jugal contacts the postorbital dorsomedially, the palatine ventromedially, the pterygoid posteriorly, and the maxilla ventrally.

STRUCTURES OF MEDIAL PROCESS: The jugal forms part of the posterior wall of the fossa orbitalis, which in UA 9748 has a posterior enlargement that is diagnostic for bothremydids ( Gaffney et al., 2006).

QUADRATOJUGAL

PRESERVATION: The quadratojugals are not preserved.

SQUAMOSAL

PRESERVATION: Both squamosals are missing, although some of the sutural surfaces remain on the preserved quadrates and opisthotics.

POSTORBITAL

PRESERVATION: Both postorbitals are present, although they lack their posterior limits and some of their ventral margins.

CONTACTS OF LATERAL PLATE: The postorbital in UA 9748 contacts the frontal anteromedially, the jugal ventrally, and the parietal posteromedially. The lateral views of UA 9748 in figure 3 are somewhat misleading, as the frontal does enter the orbital margin, but in these figures the (displaced) postorbital appears to exclude the frontal.

STRUCTURES OF LATERAL PLATE: The postorbital in UA 9748 forms the dorsal part of the orbital margin, as in the other Kurmademydini . The degree to which or even whether it entered the temporal margin is not determinable, although presumably it did, based on the small edge of parietal preserved.

CONTACTS OF MEDIAL PROCESS: In the septum orbitotemporale, facing the fossa orbitalis, the postorbital contacts the frontal dorsomedially, the jugal ventrolaterally, and the parietal medially. There is no palatine contact as seen in Kurmademys . In the septum orbitotemporale, facing the fossa temporalis, the postorbital contacts the parietal dorsomedially and the jugal ventrolaterally. Possibly there was a pterygoid contact, now broken away. There is no palatine contact.

STRUCTURES OF MEDIAL PROCESS: The postorbital forms part of the roof and lateral wall of the sulcus palatinopterygoideus and septum orbitotemporale, as in other bothremydids.

PREMAXILLA

PRESERVATION: The premaxillae are not preserved.

MAXILLA

PRESERVATION: Both maxillae are present and nearly complete in UA 9748. Their edges are missing at the premaxillary sutures and the pterygoid and palatine contacts are mostly broken edges. Additionally, there are five referred maxillae (FMNH PR 2650, FMNH PR 2651, FMNH PR 2652, UA 8652, and UA 8655) that probably belong to this species.

CONTACTS OF VERTICAL PLATE: The maxilla in UA 9748 contacts the premaxilla (presumably) anteromedially, the jugal posterodorsally, and the prefrontal anterodorsally.

STRUCTURES OF VERTICAL PLATE: The maxilla forms a distinct ridge separating the fossa orbitalis from the external surface of the skull, as in Kurmademys and in contrast to other bothremydids such as Bothremys . The ridge is more rounded in UA 9748 and more acute in

[C. Li, del.]

Kurmademys . The extent and shape of the apertura narium externa and foramen orbitonasale are not determinable, but the preserved areas are consistent in morphology with those of Kurmademys . The maxilla forms the ventral part of the anterior cheek emargination.

CONTACTS OF HORIZONTAL PLATE: The maxilla in UA 9748 contacts the palatine posteromedially and the jugal posterolaterally.

STRUCTURES OF HORIZONTAL PLATE: The triturating surface of Kinkonychelys is very similar to that in Kurmademys . It is triangular, wide posteriorly, and with no pits or ridges. The palatine makes up a significant part of it posteromedially, as in Kurmademys . The labial ridge in UA 9748 is thicker and less acute than in Kurmademys .

VOMER

PRESERVATION: The vomer is not preserved.

PALATINE

PRESERVATION: The palatines are incomplete in UA 9748 and not as well preserved as the other cranial elements. Those portions of the palatines forming part of the triturating surfaces are preserved, but they are broken off close to the maxillae on both sides. On the right side, some of the palatine is attached to the right pterygoid, extending anteriorly to form a broad area of contact between these two pieces of the right palatine. However, the more complex contacts of the bone are either missing or poorly preserved.

TABLE 1 Comparison of Tribe Kurmademydini Skulls

CONTACTS: The palatine contacts the maxilla anterolaterally, the other palatine medially, and the pterygoid posteriorly. There does not seem to be a parietal or postorbital contact.

STRUCTURES ON DORSAL AND VENTRAL SUR- FACES: The palatine forms the medial part of the fossa orbitalis floor and the lateral edge of the apertura narium interna. There is no dorsal process to the parietal as in Kurmademys (the Sankuchemys condition is unknown). The anterior margin of the foramen palatinum posterius can be seen on the right palatine, presumably the posterior edge of the foramen was formed by the pterygoid. The palatine forms the posteromedial part of the triturating surface, as in other Kurmademydini ( Gaffney, 2006) .

QUADRATE

PRESERVATION: Both quadrates are present in UA 9748, but the left one is more complete.

The left one has its anterior limits marked by broken edges while the right one has a section of natural edge showing some of the cheek emargination. Between the two quadrates, nearly all of the cavum tympani and quadrate portion of the antrum postoticum can be determined. The medial parts of both quadrates are preserved, although the right one has some breakage around the fossa pterygoidea.

CONTACTS ON LATERAL SURFACE: Due to lack of preservation, the only definite lateral surface contact of the quadrate in UA 9748 is with the squamosal posterodorsally. However, extensive cheek and temporal emargination suggest that the only other likely contact is with the quadratojugal anterodorsally, as in Kurmademys , which has a very similar skull emargination.

STRUCTURES ON LATERAL SURFACE: As stat- ed above, the best estimate for cheek and

O 53.05

a

N 15.8

M 15.05

L 9.01

) K 24.00

315

.

fig 2 J a

: 11.0

2006

.

,

1

J 11.8

al et

.

Gaffney I indet

2 see

(

H 41.05

TABLE rogersi G 30.00 Kinkonychelys F. indet of

E 15.05 Measurements

1

2 D a 12.8

D 11.09

C 13.04

B 60.04

a

A 53.9

. 9748 Damaged UA a temporal emargination in Kinkonychelys suggests an extensive degree for both, similar to that seen in Kurmademys .

The cavum tympani is almost completely known for UA 9748. The incisura columellae auris is completely enclosed by bone and separated from the eustachian tube, both bothremydid synapomorphies ( Gaffney et al., 2006). There is a narrow groove extending posteriorly on a ridge from the incisura to the sulcus eustachii on the back of the quadrate, a feature of Kurmademys and Galianemys (Cenomanian, Morocco). The antrum postoticum is incomplete due to the absence of much of the squamosal, but its width and depth can still be determined from the quadrate portions. The cavum tympani of Kinkonychelys is most similar to that in Kurmademys .

The fossa precolumellaris is large, deep, and well defined in Kinkonychelys ; the condition occurring in Pelomdusoides outgroups but found only in Kurmademys among the Bothremydidae (unknown for Sankuchemys ). The two Kinkonychelys specimens, UA 9748 and FMNH PR 2446, differ significantly in the position of this fossa. In UA 9748 it is ventral to the incisura columellae auris, but in FMNH PR 2446, it is anterior to the incisura. To our knowledge, this degree of variation is unknown within a single species among the Recent species of podocnemidids.

CONTACTS ON DORSAL AND ANTERIOR SUR- FACE: As in other Pelomedusoides the contacts of the quadrate in Kinkonychelys are with the prootic anteromedially, the opisthotic posteromedially, the supraoccipital medially, and the squamosal posteriorly and posterolaterally.

STRUCTURES ON DORSAL AND ANTERIOR SUR- FACE: One of the more obvious characters of bothremydids is the unusual migration of the foramen stapediotemporale from the dorsal surface of the otic chamber onto the anterior surface. Kurmademys is unique among bothremydids in having the primitive position of the foramen on the dorsal surface, but Kinkonychelys exhibits this condition as well.

CONTACTS ON VENTRAL SURFACE: As in other bothremydids, the quadrate contacts in UA 9748 are with the pterygoid anteromedially, the basisphenoid medially, and the basioccipital posteromedially. In Kurmademys and Sankuchemys the prootic is exposed ventrally and contacts the quadrate medially. This is also the case in FMNH PR 2446, the specimen referred below to Kinkonychelys sp. In Kinkonychelys rogersi , however, the prootic is covered, mostly by a thin flange of quadrate (visible in the broken area of the right side), so it is not exposed ventrally.

STRUCTURES ON VENTRAL SURFACE: The quadrate forms the lateral wall of the fossa pterygoidea (see Pterygoid). The condylus mandibularis in Kinkonychelys lies close to the level of the condylus occipitalis, more posterior than the condylus mandibularis in the other Kurmademydini , which is much more anterior with respect to the condylus occipitalis.

CONTACTS ON POSTERIOR SURFACE: As in other bothremydids, the contacts in Kinkonychelys are with the squamosal dorsolaterally, the opisthotic dorsomedially, the exoccipital medially, and the basioccipital ventromedially.

STRUCTURES ON POSTERIOR SURFACE: The quadrate forms the lateral portion of the fenestra postotica, which in UA 9748 is closed medially by the exoccipital. There is a low ridge separating the lateral head vein and stapedial artery. The foramen chorda tympani inferius lies on the posterior face of the condylus mandibularis.

PTERYGOID

PRESERVATION: The pterygoids in UA 9748 are both present but incomplete anterolaterally. A processus trochlearis pterygoidei is present but has no definite contact with the main pterygoid pieces.

CONTACTS ON VENTRAL SURFACE: As in other bothremydids, the pterygoid in Kinkonychelys contacts the palatine anteriorly, the other pterygoid anteromedially, the basisphenoid posteromedially, and the quadrate posterolaterally.

STRUCTURES ON VENTRAL SURFACE: The processus trochlearis pterygoidei, while associated with this specimen, cannot be definitely articulated with it, so its angle cannot be determined with certainty.

The fossa pterygoidea, the depression for attachment of the pterygoideus muscle (see Gaffney et al., 2006), is deep and well defined in UA 9748. Although the depth of the fossa is about the same in both Kurmademys and Kinkonychelys , its shape differs. In Kinkonychelys the fossa is deeper anteriorly in the area of the foramen posterius canalis carotici interni whereas in Kurmademys it becomes shallow anteriorly. Medially the basisphenoid overhangs the fossa and the foramen posterius canalis carotici interni in UA 9748 (and in FMNH PR 2446 of Kinkonychelys sp. ), but there is no such overhang in Kurmademys . In Kurmademys the prootic is exposed in the roof of the fossa but not in Kinkonychelys .

The foramen posterius canalis carotici interni in UA 9748 is formed between the basisphenoid medially and the pterygoid laterally. In Kurmademys the foramen is almost completely within the basisphenoid but very close to the pterygoid, and in Sankuchemys it is between the basisphenoid and pterygoid. In FMNH PR 2446 it is also formed between the bones. Just lateral to the foramen posterius canalis carotici interni in UA 9748 is a small foramen completely in the pterygoid that is probably for the vidian nerve. This is also the condition in Kurmademys ( Gaffney et al., 2006: fig. 63). The facial nerve is always contained within the prootic bone in pleurodires, although this is frequently covered by other bones and not visible on the skull surface ( Gaffney et al., 2006). In Kurmademys and Sankuchemys the prootic is exposed and the foramen nervi facialis is visible on the ventral surface. However, in UA 9748 the pterygoid has a flange that extends medially to cover the prootic and the exit of the facial nerve, so that the foramen nervi facialis is formed between the pterygoid laterally and the basisphenoid medially, with a small piece of quadrate entering the foramen posteriorly. This can be seen completely preserved only on the left side of UA 9748, but some of the internal details are visible on the damaged right side.

Another feature of the fossa pterygoidea in UA 9748 is the small overhang formed by the basisphenoid along the medial margin of the fossa. This is not seen in Kurmademys , but it is seen in FMNH PR 2446 and seems to be related to the greater depth of the fossa anteriorly in these two taxa.

CONTACTS ON DORSAL SURFACE: The area around the base of the processus trochlearis pterygoidei is damaged or missing in UA 9748 and the contacts are not preserved. The other pterygoid contacts are with the parietal anterodorsally, the prootic posterodorsally, the quadrate posterolaterally, the palatine anteriorly, and the basisphenoid medially, as in other bothremydids.

STRUCTURES ON DORSAL SURFACE: Although the anterior edges of the pterygoids are broken, the right crista pterygoidea is nearly complete and the left one is mostly complete. The foramen nervi trigemini is formed at the posterior end of the crista and has the usual bones in its margin: the pterygoid ventrally, the parietal anterodorsally, and the prootic posterodorsally. Medial to the foramen nervi trigemini and the crista pterygoidea is the canalis cavernosus posteriorly and the sulcus cavernosus anteriorly. If a foramen caroticum laterale were present it would be in the sulcus cavernosus, but there is no sign of one. There is also no sign of the anterior opening of the vidian nerve, which should be in this area, but it is possible that the pterygoid is broken off too far posteriorly for the foramen to be preserved.

SUPRAOCCIPITAL

PRESERVATION: The supraoccipital is present in UA 9748, but only the ventral half is preserved; there is nothing of the crista supraoccipitalis left and no portion of the skull roof contribution.

CONTACTS: The supraoccipital in UA 9748 has contacts with the parietals dorsally and anteriorly, the prootic anterolaterally, the opisthotic posterolaterally, and the exoccipitals posteroventrally. Most bothremydids also have a lateral contact with the quadrate ( Gaffney et al., 2006) and this seems likely in UA 9748. However, the area is damaged, so the character has been coded as ‘‘?’’ in the data set. This contact is actually a thin sheet of supraoccipital overlying the prootic and opisthotic and is easily damaged.

STRUCTURES: The foramen magnum is rimmed dorsally by the supraoccipital and ventrally by the exoccipitals. The crista supraoccipitalis is missing, but what is preserved is consistent with that of Kurmademys .

EXOCCIPITAL

PRESERVATION: Both exoccipitals are present but slightly damaged. The right one is missing more of the foramen magnum margin but has the condylus occipitalis preserved, while the left one is missing the condylus but preserves most of the margin of the foramen magnum. The ventral and occipital areas are all present.

CONTACTS: As in other bothremydids, the contacts of the exoccipital in Kinkonychelys are with the supraoccipital dorsally, the opisthotic laterally, the quadrate ventrolaterally, and the basioccipital ventrally.

STRUCTURES: The condylus occipitalis in UA 9748 is made up of the exoccipitals only; the basioccipital does not contribute to it. This is determinable, even though only the right exoccipital has the condylus preserved, because the preserved portion of the exoccipital makes up half of the condyle. Kurmademys has the basioccipital in the condylus occipitalis, but FMNH PR 2446, the other Madagascar braincase, also has only the exoccipitals making up the condyle.

The foramen nervi hypoglossi is best seen on the right side of UA 9748 and it consists of three openings. The two more dorsal ones are recessed on a larger depression, and the third is more ventral, in the basioccipital suture. Kurmademys has two foramina on each side and no recess, as is the condition in FMNH PR 2446. These foramina tend to vary individually, so their systematic significance is dubious.

The foramen jugulare posterius is closed and completely formed by the exoccipital in Kinkonychelys , as it is in Kurmademys . In FMNH PR 2446, however, the opisthotic forms the lateral wall to close the foramen.

The fenestra postotica in UA 9748 is closed with a small portion of the exoccipital forming its most medial edge.

BASIOCCIPITAL

PRESERVATION: The basioccipital in UA 9748 is nearly complete, although the small triangular piece that would fit in the neck of the condylus occipitalis is broken off and there is a crack down the middle.

CONTACTS: As in the other bothremydids, the contacts of the basioccipital in Kinkonychelys are with the basisphenoid anteriorly, the quadrate laterally, the exoccipitals posterodorsally, and the quadrate laterally. The exoccipital-quadrate contact is a bothremydid synapomorphy ( Gaffney et al., 2006).

STRUCTURES: The basioccipital does not form part of the condylus occipitalis, but does seem to enter its neck. The tuberculum basioccipitale of the Kurmedemydini is very low but widely spaced and this is also the case for Kinkonychelys . The shape is very similar to that in Kurmademys but in contrast to the longer basioccipital of Sankuchemys .

PROOTIC

PRESERVATION: Both prootics are preserved in UA 9748. The right one is more damaged than the left, which is nearly complete. Some of the breakage of the right allows observation of internal morphology.

CONTACTS: As in the other bothremydids, the contacts of the prootic in UA 9748 are with the parietal dorsomedially, the quadrate laterally, the supraoccipital posterodorsally, and the pterygoid and basisphenoid ventrally. Possibly there is a contact with the opisthotic posteriorly, but this may be prevented by a supraoccipitalquadrate contact (see supraoccipital).

STRUCTURES: The prootic forms the anterodorsal margin of the foramen nervi trigemini and the medial margin of the foramen stapediotemporale, as in other bothremydids. As discussed elsewhere (see Pterygoid, Quadrate), the prootic of Kinkonychelys is unusual among the Kurmademydini in not being exposed in the roof of the fossa pterygoidea. As a result, the foramen nervi facialis, usually formed by the prootic, is formed by the pterygoid and basisphenoid in Kinkonychelys . Interestingly, in the very similar FMNH PR 2446 of Kinkonychelys sp. , the prootic is exposed ventrally and forms the foramen nervi facialis along with the basisphenoid.

OPISTHOTIC

PRESERVATION: Both opisthotics are present in UA 9748; the left one is nearly complete, but the right one lacks its posterior end. The medial sutures are in broken areas and unclear.

CONTACTS: As in the other bothremydids, the contacts of the opisthotic in Kinkonychelys are with the supraoccipital anteromedially, the quadrate anterolaterally, the squamosal posterolaterally, and the exoccipital posteromedially. Possibly there is a prootic contact anteriorly (see Supraoccipital).

STRUCTURES: The foramen jugulare posterius in UA 9748 has no opisthotic contribution. The adjacent fenestra postotica is formed medially by the exoccipital, dorsally by the opisthotic, and ventrally and laterally by the quadrate. As with the other basicranial elements, the internal structures, such as the cavum labyrinthicum, the hiatus acusticus, and the cavum acusticojugulare are visible, but do not differ significantly from previously described material of bothremydids (see Gaffney et al., 2006).

BASISPHENOID

PRESERVATION: Most of the basisphenoid is present in UA 9748, but on the midline some bone is missing and the right fossa pterygoidea has a broken roof with parts of the pterygoid, basisphenoid, and quadrate missing.

CONTACTS: On the ventral surface, the basisphenoid in UA 9748 has the usual bothremydid contacts with the pterygoids anterolaterally, the basioccipital posteriorly, and the quadrate laterally. The latter contact is a synapomorphy for the superfamily Podocnemidoidea ( Podocnemididae + Bothremydidae ) of Gaffney et al. (2006).

STRUCTURES ON VENTRAL SURFACE: The most obvious feature on the ventral surface of the basisphenoid is the prominent fossa pterygoidea, a feature also occurring in FMNH PR 2446 and Kurmademys but otherwise rare in bothremydids. In the anterior wall of the fossa, the foramen posterius canalis carotici interni in UA 9748 is formed medially by the basisphenoid, as in FMNH PR 2446. The medial wall and the small overhang of the fossa pterygoidea are also formed by the basisphenoid in UA 9748 (see Pterygoid).

CONTACTS ON DORSAL SURFACE: As in other bothremydids, the contacts of the basisphenoid in Kinkonychelys are with the pterygoid anterolaterally, the prootic laterally, the palatines anteriorly (only on the dorsal surface), and the basioccipital posteriorly.

STRUCTURES ON DORSAL SURFACE: Fortunately, there are specimens of both Kurmademys ( Gaffney et al., 2006) and FMNH PR 2446 that show the dorsal surface of the basisphenoid for comparison with UA 9748. The rostrum basisphenoidale in UA 9748 and FMNH PR 2446 is broken off. The sella turcica is preserved and very similar to that of Kurmademys in being relatively wide with the foramen anterius canalis carotici interni at the posterolateral corners of the sella turcica. The processus clinoideus is a low process with the foramen nervi abducentis (VI) penetrating its base, as in Kurmademys .

LOWER JAW

A lower jaw ramus, FMNH PR 2653, consisting mostly of the dentary, is readily identifiable as a bothremydid based on the very low labial ridge, the posteriorly rising lingual ridge forming a shallow concavity laterally, with a symphysis having a U-shaped concavity posterior to a narrow triturating surface (see Gaffney et al., 2006, for the lower jaw morphology of bothremydids). The ramus is very similar to those described for Kurmademys (Late Cretaceous, India) and Cearachelys (Early Cretaceous, Brazil), the presumed primitive condition for bothremydids. The position and shape of the coronoid bone is the same in both. The sulcus cartilaginis meckelii is anteriorly continuous with the symphyseal depression, also as in other bothremydids. Although it is impossible to be sure, it is very likely that this jaw belongs to Kinkonychelys , based on agreement in triturating surface shape and size.

DISCUSSION

Kinkonychelys is a bothremydid because it has the diagnostic characters of an exoccipitalquadrate contact and a fully enclosed incisura columellae auris ( Gaffney et al., 2006). Kinkonychelys belongs to the tribe Kurmademydini , previously known to include only Sankuchemys and Kurmademys from the Late Cretaceous of India, because it has a deep fossa pterygoidea, a foramen stapediotemporale facing dorsally, a jugal not retracted from the orbit, a deep fossa precolumellaris, and a large, wide antrum postoticum. It agrees with FMNH PR 2446 of Kinkonychelys sp. (described below) in the form of the overlapping fossa pterygoidea, which is unique.

FAMILY BOTHREMYDIDAE BAUR, 1891

TRIBE KURMADEMYDINI GAFFNEY, TONG, AND MEYLAN, 2006

Figures

Fig. 2. Kinkonychelys rogersi, n. gen. et sp. UA 9748, holotype skull. A, Dorsal; B, ventral; C, right lateral; D, anterior; E, left lateral; F, posterior. [C. Li, del.]

Fig. 3. Kinkonychelys rogersi, n. gen. et sp. UA 9748, holotype skull. A, Dorsal; B, ventral; C, right lateral; D, anterior; E, left lateral; F, posterior. Key to Fig. 2. [C. Li, del.]

Fig. 4. Kinkonychelys rogersi, n. gen. et sp. UA 9748, holotype. Partially restored ventral view of skull.

Fig. 8. Medial views of cavum cranii in two skulls of Kinkonychelys. A, C, Kinkonychelys rogersi, n. gen. et sp., UA 9748, holotype; B, D, Kinkonychelys sp., FMNH PR 2446. Anterior to the right. [I. Kayama, F. Ippolito, del.]