Galianemys emringeri

GAFFNEY, EUGENE S, TONG, HAIYAN & MEYLAN, PETER A, 2006, EVOLUTION OF THE SIDE-NECKED TURTLES: THE FAMILIES BOTHREMYDIDAE, EURAXEMYDIDAE, AND ARARIPEMYDIDAE, Bulletin of the American Museum of Natural History 300 (300), pp. 1-698 : 233-250

Galianemys emringeri and Galianemys whitei

In this section, both species of this genus are described together. The Galianemys species are quite similar to each other, and it makes sense to the senior author to combine the descriptions to avoid repetition. Galianemys is described and figured more extensively than some other taxa because it is a comparatively generalized bothremydid, known from a relatively large array of good material. The two species are represented by a total of 13 skulls, 6 of G. emringeri and 7 of G. whitei (table 9). Of these, G. whitei has six relatively complete skulls, and G. emringeri has three relatively complete skulls. Character variation in the genus is listed in table 9. In addition to the figures grouped with the descriptions (figs. 81–100), the reader should be aware of other Galianemys figures in the character descriptions section: figure 277 (foramen posterius canalis carotici interni), figure 278 (septum orbitotemporale), figure 280 (orbital floor), and figure 284 (quadrate). Much of this section is modified from Gaffney, Tong, and Meylan (2002) by the addition of new material and more comparisons. Galianemys is also shown in a series of CT scans on the DigiMorph University of Texas website: http://www.digimorph.org/ specimens/ Galianemys_emringeri /.

Galianemys is most closely related to Cearachelys . They make up the tribe Cearachelyini .

PREFRONTAL (figs. 81, 89, 97)

Preservation: The prefrontal is preserved in Galianemys whitei in AMNH 30036, 29987, 29986, 30028, 30027, 30555, and in MDEt 45. In Galianemys emringeri it is preserved in AMNH 30035, 30037, 29985,

and 30040. It can be seen particularly well in AMNH 30027 and 29986 where the left prefrontal is lost, allowing the internal surfaces on the right side to be seen.

Contacts: As in Pelusios and all other Pelomedusoides, the prefrontal in both species of Galianemys contacts the maxilla anteroventrolaterally, the frontal posteriorly, and the other prefrontal medially. In Galianemys emringeri the prefrontal-frontal suture trends posteromedially for a short distance medial to the orbital margin, then trending anteromedially to form a midline projection of the frontal. In G. whitei the suture is nearly straight in AMNH 29986, 29987, 30036, 30027, 30555, and in MDEt 45. In AMNH 30028 the suture is asymmetric with the frontal projecting anteriorly on the right side but not on the left. Cearachelys and Kurmademys have an anteriorly convex suture, but it is nearly straight in Bothremys and Rosasia and slightly curved in other genera.

Structures: The prefrontal in Galianemys is similar to that in other Pelomedusoides. The dorsal plate forms the anterodorsal margin of the orbit and the dorsal margin of the apertura narium externa. The margin is slightly protruding over the apertura in Galianemys , as in most Pelomedusoides, but there is some variation within the available specimens. A specimen of Galianemys whitei, AMNH 29987, has a much thicker margin that forms a slightly concave profile in lateral view rather than convex, as in all the other skulls. The skulls of G. emringeri and G. whitei do not differ consistently in the prefrontal. The prefrontal in Galianemys is very similar to that bone in Cearachelys and Kurmademys .

FRONTAL (figs. 81, 89, 97)

Preservation: The frontal in Galianemys whitei is preserved in AMNH 29987, 29986, 30036, 30027, 30028, 30555, and in MDEt 45.

In Galianemys emringeri it is preserved in AMNH 30037, 30040, 30035, and 29985. It is most visible in AMNH 30027, 29986, and 30037.

Contacts: The frontal contacts in Galianemys are with the prefrontal anteriorly, postorbital posterolaterally, parietal posteriorly, and the other frontal medially. These are the same in both Galianemys species and in Cearachelys .

Structures: The frontal is very similar in both Galianemys and Cearachelys . The ridge defining the sulcus olfactorius is deeper in Galianemys than in Cearachelys . There is some variation in this feature among the Galianemys specimens, but they are all deeper than in Cearachelys , Kurmademys , and the Pelomedusidae . The interorbital width is wider in Galianemys than in Cearachelys , Kurmademys , and the Pelomedusidae . This is the result of a greater overhang of the frontal over the fossa orbitalis lateral to the sulcus olfactorius.

PARIETAL (figs. 81, 89, 97)

Preservation: The parietal is preserved to some extent in all the Galianemys specimens. It is complete in AMNH 30028 and 30555 and is nearly complete in AMNH 29987 (all Galianemys whitei ). In Galianemys emringeri, AMNH 30037 has the most complete parietals.

Contacts of dorsal plate: The parietal contacts in Galianemys are with the frontal anteriorly, the postorbital anterolaterally, and with the other parietal medially.

Structures of dorsal plate: The degree of emargination in Galianemys is similar to that seen in Cearachelys but is not as extensive. Kurmademys and the pelomedusids have the most extreme emargination, with Cearachelys being more covered and Galianemys more covered than Cearachelys . The temporal skull roof consists largely of parietal and postorbital. Galianemys is more emarginate than Foxemys . The other bothremydids do not have complete preservation of the roof for comparison.

In contrast to Cearachelys , Kurmademys , and pelomedusids, the parietal of Galianemys is wider posteriorly near the midline along the supraoccipital contact. Although the temporal emargination depth is not much less than in Cearachelys , the temporal opening in Galianemys is more covered due to the wider parietal roof along its posterior extension.

Contacts of processus inferior parietalis: The processus inferior parietalis (fig. 97) contacts the palatine anteroventrally, the pterygoid ventrally, the prootic posteroventrally, and the supraoccipital posteriorly, as in Cearachelys , the other Pelomedusoides, and most turtles.

Structures of processus inferior parietalis: The palatine has a dorsal extension, higher than the crista pterygoidea, so the processus inferior parietalis is deeper posteriorly than anteriorly. The processus is relatively long in contrast to most Taphrosphyini but like Phosphatochelys . The parietal forms the anterodorsal margin of the foramen nervi trigemini.

JUGAL (figs. 81, 89, 278, 280)

Preservation: The jugal is preserved in all specimens of both species of Galianemys . In AMNH 29985, the type of Galianemys emringeri , the jugal is incomplete posteriorly, but in AMNH 30037 and 30035 it is complete.

Contacts of lateral plate: The jugal in Galianemys contacts the postorbital dorsally, the maxilla anteroventrally, and the quadratojugal posteroventrally. These are as in Cearachelys except that the jugal of Galianemys is completely separated from the orbital margin by a wide postorbital-maxilla contact.

Structures of lateral plate: The jugal of Galianemys is excluded from the orbital margin by a postorbital-maxilla contact and is excluded from the cheek margin by a quadratojugal-maxilla contact.

Contacts of medial process: The medial jugal process is exposed in the orbital floor and the septum orbitotemporale (figs. 278, 280). In the orbital floor it contacts the maxilla anteriorly and anterolaterally, the palatine medially, and the postorbital posterodorsally. The postorbital and maxilla have a strong lateral contact widely separating the jugal exposure in the orbital floor from the cheek jugal exposure. In Cearachelys the postorbital and maxilla barely meet along the orbital margin barely separating the two parts of the jugal. The jugal is widely exposed on the orbital margin in Kurmademys and pelomedusids. The jugal is also exposed in the septum orbitotemporale. On its posterior surface, the jugal contacts the postorbital dorsomedially, the pterygoid posteromedially, and the maxilla anteroventrally. In Galianemys whitei the jugal also contacts the palatine ventromedially but in Galianemys emringeri this contact is smaller (AMNH 30037, 30035) or absent (AMNH 29985), and the maxilla and pterygoid are closer to each other.

Structures of medial process: The medial process of the jugal floors the orbit and forms part of the postorbital wall. In Galianemys emringeri the jugal is restricted to the vertical surface of the wall, but in G. whitei the jugal curves anteriorly and forms a small part of the triturating surface. This area of the triturating surface has a shallow but definitive depression in G. whitei , but it is flat in G. emringeri .

QUADRATOJUGAL (figs. 81, 89)

Preservation: The quadratojugal is present in Galianemys whitei specimens at least in part in AMNH 30036 and 29986, but it is most complete in AMNH 30028, 30555, and 29987. In Galianemys emringeri the quadratojugal is almost complete in AMNH 30035 and partial in AMNH 30037 and 30040.

Contacts: The quadratojugal contacts the maxilla anteroventrally, preventing exposure of the jugal on the ventral edge of the skull and producing the complete absence of a cheek emargination. Anteriorly the quadratojugal contacts the jugal and anterodorsally it contacts the postorbital. Posteriorly the quadratojugal has a long S-shaped contact with the quadrate; above this a narrow posterior process of the quadratojugal meets a narrow anterior process of the squamosal (preserved in AMNH 30040 and 30035 of Galianemys emringeri ).

Structures: The quadratojugal is a large, flat plate that forms about half of the cheek in Galianemys . Cheek emargination as seen in Kurmademys is completely absent, and even the slight emargination seen in the cheek of Cearachelys is absent. Otherwise, the quadratojugal of Galianemys is very similar to that in Cearachelys in contacts, size, and shape.

SQUAMOSAL (figs. 81, 88, 89, 98, 284)

Preservation: The squamosal is present in AMNH 30037, 30040, and 30035 in Galianemys emringeri , and in AMNH 30028, 30027, 30036, 30555, 29987, and 29986 in Galianemys whitei .

Contacts: Squamosal contacts do not vary much in Pelomedusoides. The conical squamosal fits on the quadrate, contacts the opisthotic medially, and has a short anterior process reaching the quadratojugal anterodorsally.

Structures: The cone shape of the squamosal in Galianemys is very similar to that seen in Cearachelys . There is no vertical flange on its ventral surface, as in Taphrosphys .

POSTORBITAL (figs. 81, 89, 278)

Preservation: At least some of the postorbital is present in four Galianemys emringeri specimens and all seven Galianemys whitei skulls. Nearly complete postorbitals are in AMNH 30035, 30040, and 30037 for G. emringeri and AMNH 30028, 30555, and 29987 for G. whitei .

Contacts of lateral plate: The lateral plate of the postorbital forms part of the temporal roof and in Galianemys contacts the frontal anteromedially, the parietal posteromedially, the maxilla anteroventrally, the jugal ventrolaterally, and the quadratojugal posterolaterally.

Structures of lateral plate: The postorbital lateral plate forms most of the posterior orbital margin and extends posteriorly to reach the edge of the temporal margin.

Contacts of medial process: The medial process is exposed on both sides of the septum orbitotemporale with these contacts: palatine ventromedially, jugal ventrally, maxilla ventrolaterally, and frontal dorsomedially. In posterior view of the septum (fig. 278) the medial process of the postorbital has these contacts: parietal dorsomedially, jugal ventrolaterally, and pterygoid ventromedially. The strong postorbital-maxilla contact that broadly excludes the jugal from the orbital margin is unique among pleurodires.

Structures of the medial process: The medial process of the postorbital forms part of the roof and the lateral wall of the sulcus palatinopterygoideus and most of the septum orbitotemporale. All of these structures are very similar in Galianemys and Cearachelys .

PREMAXILLA (figs. 81, 82, 89, 96)

Preservation: The premaxilla is present in AMNH 30035 and 30037 in Galianemys emringeri , but in Galianemys whitei only the presumed juvenile, MDEt 45, and AMNH 30555, have the premaxilla preserved. This is unfortunate because, as preserved, this bone differs in the two species.

Contacts: The usual posterolateral contacts with the maxilla and with the other premaxilla on the midline occur in all four specimens. In AMNH 30037 and 30035 the vomer is not preserved and the premaxilla ends in a free margin on the apertura narium interna. But in MDEt 45 and AMNH 30555, the vomer is present and contacts the posteromedial margins of both premaxillae.

Structures on dorsal surface: In all four specimens the anterior margins of the premaxillae are broken, but they form the ventral margin of the apertura narium externa. In AMNH 30037 the premaxilla forms a high median ridge on the midline contact of the premaxillae, not seen in Cearachelys but similar to one in Kurmademys , partially dividing the fossa nasalis into paired choanal troughs. This ridge is not developed in MDEt 45, although whether this could be growth related is unknown. The ridge is not preserved in AMNH 30555.

Structures on ventral surface: The ventral surface of the premaxilla forms part of the labial ridge and the triturating surface. The premaxillary parts of these, as seen in the specimens available, are significantly different. In Galianemys emringeri, AMNH 30035 and 30037, the ridge is very thick, deep, and blunt. In Galianemys whitei , MDEt 45 and AMNH 30555, it is thin, shallow, and acute. Some degree of this variation is presumed to persist in the adult because G. emringeri has a thicker and blunter labial ridge than does G. whitei . In AMNH 30037 the premaxilla has the thick labial ridge anteriorly; posterior to that is an inclined triturating surface; and posterior to that is a more inclined surface forming a deep median concavity. Where the two surfaces meet, the foramen praepalatinum penetrates the bone. In MDEt 45 the foramen is visible on each side, but the entire surface posterior to the labial ridge is flat; there is no inclination and no median concavity. In MDEt 45, a medial process of the maxilla reaches the vomer to prevent the premaxilla from reaching the apertura narium interna. It is, of course, possible that MDEt 45 is yet a third species distinct from G. emringeri and G. whitei , but it does agree with G. whitei in other features.

MAXILLA (figs. 81, 82, 89, 90, 97, 280)

Preservation: The maxilla is present and nearly complete in all seven Galianemys whitei skulls and in four of the Galianemys emringeri skulls (AMNH 30037, 29985, 30035, and 30040); most show the sutures clearly.

Contacts of vertical plate: The vertical plate of the maxilla contacts the premaxilla anteromedially, the postorbital posterodorsally, the jugal posterodorsally (posterior to the postorbital), and the quadratojugal posteriorly.

Structures of vertical plate: The vertical plate of the maxilla forms the ventral orbital margin, the labial ridge of the triturating surface, and the anterior part of the cheek. The dorsal process of the maxilla lies between the apertura narium externa, and the orbit and is similar in size to that in Cearachelys , but thicker than in Kurmademys .

The snout just anterior to the orbit of some Galianemys specimens is more pinched, bent toward the midline, than others. In AMNH 29987 the pinching is most pronounced but other skulls of Galianemys whitei, AMNH 30036, 30028, 30555, and 29986, do not show this. This area of the maxilla in AMNH 29987 is rugose, and the pinching may be a pathology or just individual variation. The degree of pinching, however, is the same on both sides. In Galianemys emringeri there is a slight pinching of the snout in the same area, but not to the extent seen in AMNH 29987. At present we interpret this as an individual variation of AMNH 29987.

Contacts of horizontal plate: The horizontal plate (in ventral view) contacts the premaxilla anteromedially, the palatine posteromedially, and the jugal posteriorly. Among the 10 Galianemys skulls, the vomer is preserved in AMNH 30555 (fig. 96), G. whitei , and MDEt 45, a presumed juvenile of G. whitei . In both specimens the maxilla on both sides sends a process medially to meet the vomer and prevent the premaxilla from reaching the margin of the apertura narium interna. The condition is not determinable in either Cearachelys or Kurmademys .

Structures of horizontal plate: The horizontal plate of the maxilla forms the floor of the orbit in dorsal view (fig. 280). The maxilla forms the ill-defined lateral edge of the foramen orbito nasale, as in Cearachelys and other Pelomedusoides.

The horizontal plate in ventral view forms most of the triturating surface (figs. 82, 90). The triturating surface in Galianemys is very similar to that in Cearachelys in width and shape. It is slightly narrower than in Kurmademys . The labial ridge in Galianemys is distinctly thicker in both species than in Cearachelys and Kurmademys . The ridge is also thicker in Galianemys emringeri than in Galianemys whitei . In AMNH 30035 the ridge is thicker than in any other Galianemys specimen, but AMNH 29985 and 30037, the other two G. emringeri skulls, also have a thicker labial ridge than in any G. whitei skull. The type of G. whitei, AMNH 29987, has the thickest labial ridge in that species but it is still narrower than any of the G. emringeri skulls. Also, the labial ridge in G. whitei is relatively straight, but in G. emringeri , particularly AMNH 30035 and 30037, the ridge has a slight medial trend anteriorly, making it thicker there.

At this point we note that AMNH 30035 (figs. 81–84) differs from other Galianemys emringeri skulls in being much larger, wider, more robustly ossified, and in having thicker labial ridges. Because it has the other features of G. emringeri , we include it in this species. The maxilla of this skull is particularly distinct in its more massive form and ossification.

The triturating surface is flat in the skulls of Galianemys emringeri , but in G. whitei there is a very shallow concavity formed mostly by the jugal, which is exposed on the triturating surface in this species. The palatine forms a significant part of the triturating surface in Galianemys , as in Cearachelys and Kurmademys .

VOMER (figs. 89, 96)

Preservation: The vomer is present only in two specimens of Galianemys , MDEt 45 and AMNH 30555, both Galianemys whitei .

Contacts: The vomer contacts the premaxilla anteriorly, the maxilla anterolaterally, and the palatines posteriorly.

Structures: The vomer in Galianemys is slightly narrower than in Cearachelys , but it is expanded at both ends and separates the apertura narium interna. In contrast to most turtles that have the paired foramen praepalatinum on the vomer near the premaxilla suture, in Galianemys the foramina are in the middle of the premaxilla and not in the vomer.

PALATINE (figs. 81, 82, 89, 90, 97)

Preservation: The palatine is present in all seven Galianemys whitei skulls and in four of the Galianemys emringeri skulls. It is missing in MDEt 46 and AMNH 30026. Only MDEt 45 has the thin, original anterior margin completely preserved.

Contacts: The palatine contacts the vomer anteromedially (preserved only in AMNH 30555 and MDEt 45), the maxilla anterolaterally, the other palatine medially, the pterygoid posteriorly, and the jugal posterolaterally (except in AMNH 29985, see Jugal). On the dorsal surface the palatine contacts the parietal posteriorly, the jugal medially, the maxilla anteromedially, and the postorbital laterally (fig. 280).

Structures on dorsal surface: On the dorsal surface the palatine forms the posteromedial part of the orbital floor and the posterior margin of the foramen orbitonasale. There is a low dorsal process that meets the processus inferior parietalis (fig. 97). Lateral to this the palatine forms the anterior floor of the sulcus palatinopterygoideus.

Structures on ventral surface: Basically a flat bone, the palatine has different relations to surrounding bones on its ventral compared with its dorsal surfaces. On the ventral surface it forms the posteromedial part of the triturating surface and the posterior part of the choanal openings. These are all similar to Cearachelys . Posterolaterally the palatine forms the medial half of the foramen palatinum posterius. The foramen lies along a strong anterolateral process that is better developed in Galianemys than in Cearachelys and Kurmademys .

QUADRATE (figs. 81, 89, 284)

Preservation: The quadrate is present in all 13 Galianemys skulls, although it is detached in MDEt 45 and incomplete in AMNH 29985. All other specimens have at least one complete quadrate.

Contacts on lateral surface: In lateral view the quadrate contacts the quadratojugal anteriorly and the squamosal posterodorsally.

Structures on lateral surface: In lateral view the quadrate in Galianemys (fig. 284) does not form part of the temporal margin due to the quadratojugal-squamosal contact. The cavum tympani and its associated structures dominate the lateral view. The cavum itself is slightly deeper in Galianemys than in Cearachelys , but as in Cearachelys , there is no fossa precolumellaris, a structure seen in Kurmademys . The incisura columellae auris is completely closed by the quadrate and separated from the eustachian tube opening by bone in Galianemys . In Cearachelys the incisura is open, but it is closed in Kurmademys as in Galianemys (see also figs. 303 and 304 for distribution of these characters). The incisura in Galianemys is a teardrop-shaped foramen with the acute tip pointed posteriorly, in contrast to the symmetric oval of Kurmademys and most bothremydids. The apex of the teardrop shape in Galianemys is continued posteriorly as a trough that opens into the sulcus eustachii (the eustachian tube notch).

The antrum postoticum in Galianemys (fig. 284) is present and completely developed and is best seen in AMNH 30037, 29985 (internally, with the squamosal removed), and 30027. Its size varies slightly but perceptibly among the available skulls. It is smaller in AMNH 29987, 30028, and 29986, all G. whitei , and larger in AMNH 29985, 30037, and 30035, all G. emringeri . This is consistent with the recognition of two species, but AMNH 30036, a specimen of G. whitei , has a larger antrum, similar to that in G. emringeri . Among other genera, the antrum postoticum of Galianemys is smaller than that in Cearachelys and much smaller than that in Kurmademys and pelomedusids. It is larger, however, than in Taphrosphys and Bothremys .

The groove for the eustachian tube, the sulcus eustachii, in Galianemys is a nearly enclosed oval trending dorsomedially to ventrolaterally (fig. 284). It is open at its lateral end. It is narrow and extends for half of the distance between the incisura collumellae auris and the edge of the cavum tympani; there is no bone covering the other half. In Kurmademys the eustachian opening is wide open laterally, not constricted. In Cearachelys the sulcus eustachii and the incisura columellae auris are confluent. In other bothremydids, such as Taphrosphys and Bothremys , the sulcus eustachii is more widely open laterally and farther separated from the incisura columellae auris.

Contacts on dorsal and anterior surface: The quadrate contacts the prootic anteromedially, the supraoccipital medially, the squamosal posterolaterally, and the opisthotic posteromedially. The supraoccipital contact occurs in most bothremydids, except the Taphrosphyini and Zolhafah .

Structures on dorsal and anterior surface: The foramen stapedio-temporale in Galianemys , formed in the quadrate-prootic suture, is on the anterior surface of the otic chamber (fig. 97), as in nearly all other bothremydids, but it is not very close to the foramen nervi trigemini, as in Bothremys and other genera. In Kurmademys this foramen is slightly more posterior, just enough to make it more visible in dorsal view. It is only slightly more anterior in Kurmademys than in pelomedusids, and we judge the condition to be the same in both and primitive with respect to all other bothremydids.

Contacts on ventral surface: In ventral view the quadrate contacts the pterygoid anteromedially, the basisphenoid medially, the basioccipital posteromedially, and the squamosal posterolaterally. In Galianemys emringeri the quadrate forms the posterior part of the deep fossa pterygoidea that exposes the prootic, so in that species there is a small quadrate-prootic contact.

Structures on ventral surface: On the ventral surface, the quadrate forms the lateral margin of the foramen posterius canalis carotici interni in Galianemys whitei , but not in G. emringeri (see Pterygoid for discussion). In G. emringeri the quadrate and the prootic form a portion of the posterior wall of the large fossa pterygoidea (see Pterygoid for discussion). The condylus mandibularis in Galianemys is very similar in both species in position and shape. The condylus mandibularis is in about the same position with

30555. [E. Ullo, del.]

respect to the condylus occipitalis in Cearachelys and Galianemys , but in Kurmademys the condylus mandibularis is more anteriorly placed. The foramen for the chorda tympani is preserved in nearly all the Galianemys skulls and it is very close to its position in pelomedusids.

Contacts in posterior view: The quadrate in Galianemys contacts the squamosal dorsolaterally, the opisthotic dorsomedially, the exoccipital medially, and the basioccipital ventromedially.

Structures in posterior view: In posteri- or view the quadrate forms a number of structures in the occipital area (figs. 87, 88, 98–100). The quadrate forms the lateral margin of the fenestra postotica and its subdivisions. In Galianemys the fenestra postotica is preserved in nine skulls. In two of these the fenestra is subdivided into smaller foramina; in the rest there may be low ridges or spurs but these do not connect to completely subdivide the fenestra. The subdivided specimens are AMNH 30037, a skull of Galianemys emringeri , and AMNH 30027, a skull of G. whitei . Neither species shows more of a tendency toward subdivision than the other among the available material. In AMNH 30037 the fenestra postotica is subdivided into two foramina, an upper one, presumably for the stapedial artery, and a lower one, presumably for the lateral head vein. In AMNH 30027, however, there are three foramina as a result of the lower foramen being further subdivided into two. One of these must be the lateral head vein, but the other is a mystery. Wow. One foramen is ventral and the other ventrolateral. In AMNH 30027 this subdivision into three foramina was present on both sides, but was broken during preparation. The other skulls of both Galianemys species have variably developed grooves or spurs that are less ossified indications of these structures. In any case, the subdivision of the fenestra postotica in Galianemys is interpreted as an individual variation. In most individuals it is open as a narrow gap from the foramen jugulare posterius to the aditus canalis stapediotemporalis, a condition also seen in Cearachelys .

PTERYGOID (figs. 81, 82, 89, 90, 97, 277)