Mogharemys, Gaffney & Meylan & Wood & Simons & De Almeida Campos, 2011
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publication ID |
https://doi.org/ 10.1206/350.1 |
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persistent identifier |
https://treatment.plazi.org/id/C95DDC2B-FFF0-5E0F-FCA3-A4979FFDD0D0 |
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treatment provided by |
Felipe |
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scientific name |
Mogharemys |
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Mogharemys Figures 48–51 View Fig View Fig View Fig View Fig
PREFRONTAL
Preservation: The prefrontal is missing in BMNH R.8440. However, it is present in the figure (Dacque´, 1912: fig. 12, actually a figure of the cast, see discussion under Mogharemys in Systematics) and the more complete cast (MB. R. 2860) of BMNH R.8440 used by Dacque´.
Contacts: In the cast the prefrontal has the usual contact with the frontal posteriorly in a position similar to that in Shweboemys pilgrimi so that the prefrontal forms the anterodorsal part of the orbital margin. The cast seems to have a ventral process contacting the maxilla, as in other podocnemidids. The presence or absence of a palatine contact is not determinable in the cast.
Structures: In MB. R. 2860 the prefrontal is longer on the midline than the frontal, being more similar in that feature to Shweboemys than to the other subtribe Stereogenyina , which have relatively shorter prefrontals. The prefrontal in MB. R. 2860 has a curved, slightly protuberant, anterior margin, as in Bairdemys and Podocnemis .
FRONTAL
Preservation: Both frontals are present in BMNH R.8440, but lack their anterior margins. The anterior contacts with the prefrontals are preserved in the cast, MB. R. 2860.
Contacts: The frontal contacts the other frontal on the midline, the postorbital posterolaterally, the parietal posteriorly, and the palatine ventrolaterally in the septum orbitotemporale (broken away on the left side of BMNH R.8440).
Structures: The frontal of Mogharemys as seen in MB. R. 2860 is wider than long, differing from most subtribe Stereogenyina , which are equidimensional or longer than wide. The frontal forms the dorsal part of the orbital margin and is exposed in the anterior wall of the septum orbitotemporale much as seen in Erymnochelys . The frontal roofs the anterior part of the sulcus orbitotemporale, as in most pelomedusids.
PARIETAL
Preservation: Portions of both parietals are preserved in both the anterior and posterior moieties of BMNH R.8440. In the Berlin cast the anterior part of both parietals are preserved, overlapping with the anterior moiety of BMNH R.8440. All of the temporal roofing is absent in both specimens and only the anterior limits of the parietal on the skull roof can be seen. The anterior portion of the processus inferior parietalis is preserved in the anterior moiety and the posteriormost part of the parietal is present on the posterior moiety, although damaged on the surface. None of the skull roof is preserved on the posterior moiety of BMNH R.8440.
Contacts of dorsal plate: The parietal in BMNH R.8440 contacts the other parietal on the midline. The frontal anteriorly and the postorbital laterally. The other skull roof contacts are not preserved.
Structures of dorsal plate: Neither BMNH R.8440 nor the Berlin cast show any indications of the skull roof margins. The sulcus palatinopterygoideus is roofed posteriorly by the parietal as in most pelomedusoides.
Contacts of processus inferior parietalis: Although incomplete, the processus in Mogharemys contacts the palatine anteroventrally, the pterygoid ventrally, the prootic posteroventrally and the supraoccipital posteriorly, as in other pelomedusoides.
Structures of processus inferior parietalis: Only a small part of the margin of the foramen nervi trigemini is preserved on the right side of BMNH R.8440. It shows the parietal forming the more dorsal margin and the pterygoid the more ventral margin, as in most pelomedusoides. Although the prootic on both sides of the posterior moiety preserves some of the foramen nervi trigemini, it does not preserve the parietal contact.
JUGAL
Preservation: The anterior part of the jugal is preserved on both sides of BMNH R.8440, but the posterior limits of the lateral plate are missing.
Contacts of lateral plate: The preserved contacts in Mogharemys are with the maxilla anteroventrally and the postorbital dorsally. The posterior margin on both sides is a broken edge.
Structures of lateral plate: The jugal in Mogharemys widely enters the orbit and forms most of its posterior margin. The preserved posterior edge of the jugal and maxilla are broken, but the bone is thin and as some of the margin is smooth, probably due to abrasion rather than a natural edge, a cheek emargination close to the preserved edge is possible.
Contacts of medial process: In the floor of the orbit in dorsal view, the jugal contacts the maxilla anteriorly and laterally and the palatine medially, as in most other pelomedusoides. In the septum orbitotemporale, in posterior view, the jugal contacts the postorbital dorsomedially, the palatine ventromedially, the pterygoid posteroventrally, and the maxilla ventrally, as in most pelomedusoides.
Structures of medial process: The jugal in Mogharemys forms only a small part of the fossa orbitalis floor, but a significant part of the septum orbitotemporale. It does not enter the triturating surface.
QUADRATOJUGAL
The quadratojugal is not preserved in either BMNH R.8440 or the Berlin cast.
SQUAMOSAL
The squamosal is not preserved in either BMNH R.8440 or the Berlin cast.
POSTORBITAL
Preservation: The postorbitals on both sides of BMNH R.8440 lack the posterior plate, so its extent in the skull roof in unknown. The Berlin cast is broken to a similar extent.
Contacts of lateral plate: The contacts in Mogharemys are with the frontal anteromedially, the jugal ventrally, the parietal posteromedially, and the maxilla anteroventrally, as in most pelomedusoides.
Structures of lateral plate: The postorbital in Mogharemys forms the posterodorsal edge of the orbital margin.
Contacts of medial process: In the septum orbitotemporale, in anterior view, the postorbital contacts the frontal dorsomedially, the jugal ventrolaterally, and the palatine ventrally. In the septum orbitotemporale, in posterior view, the postorbital contacts the parietal dorsomedially, the pterygoid ventromedially, and the jugal ventrolaterally.
Structures of medial process: The medial process of the postorbital in Mogharemys forms part of the roof and lateral wall of the sulcus palatinopterygoideus and the septum orbitotemporale, as in most pelomedusoides.
PREMAXILLA
The premaxilla is not preserved in either BMNH R.8440 or the Berlin cast.
MAXILLA
Preservation: The maxilla in BMNH R.8440 is present on both sides, but both lack their anterior limits and have no indication of a premaxilla contact. The left maxilla is more complete than the right. Both lack some of the labial ridge. The restored ventral view shows the complete extent to which the maxilla is known to combine both sides. Interestingly, the Berlin specimen provides no more information and has breakage very similar to that seen in BMNH R.8440.
Contacts of vertical plate: The only contact known for the vertical part of the maxilla in Mogharemys is with the jugal posterodorsally. In the Berlin cast, it is likely that the complete orbit on the right side has the dorsal process of the maxilla that contacts the prefrontal.
Structures of vertical plate: The outer edge of the maxilla in Mogharemys curves anteromedially to a greater extent than in Podocnemis , Erymnochelys , and Peltocephalus , but similar to the curve in Stereogenys and Shweboemys , indicating a relatively wide snout. The maxilla forms the ventral margin for the orbit. There is a distinct lip along the margin as in Cordichelys , not a smooth, rounded edge as in Brontochelys .
Contacts of horizontal plate: The maxilla of Mogharemys contacts the palatine posteromedially and the jugal posterolaterally.
Structures of horizontal plate: As preserved, the maxilla of Mogharemys does not form part of the apertura narium interna margin, but it is broken away anteriorly where this would be expected. The labial ridge of BMNH R.8440 is broken along all of its length, but it is sufficiently well preserved to show that it had a relatively narrow and acute margin. This margin is not very deep, in comparison to the condition in subtribe Stereogenyina like Stereogenys . The Berlin cast, MB. R. 2860, is preserved to almost the same extent as BMNH R.8440, and does not show any more of the maxilla. The triturating surface is wide but, as noted by Williams (1954c), there is no secondary palate in Mogharemys . The maxilla bears a secondary or accessory ridge parallel to the labial ridge. This accessory ridge is deeper and wider than those seen in Podocnemis , and has a very rugose surface seen in both specimens. The maxilla makes up over half of the triturating area surface. The palatine makes up about a third of the surface as preserved. There is no contribution from the jugal.
Although many podocnemidids have accessory ridges of varying sizes, the maxillary ridge seen in BMNH R.8440 and its cast, MB. R. 2860, is relatively broader than those seen in Podocnemis , for example. The more medial accessory ridge is formed entirely by the palatine and, parallel to the accessory ridge of the maxilla, is deeper and blunter then the accessory ridge. This combination in Mogharemys of a more massive medial maxillary ridge with a smaller but still prominent accessory ridge is unique among the Podocnemididae . Dacquemys (Dacque´, 1912; Gaffney et al., 2002) also has two prominent ridges but the more lateral accessory ridge is larger than the medial ridge.
On the dorsal surface the maxilla forms the lateral part of the floor of the fossa orbitalis as in other podocnemidids.
VOMER There is no evidence for the presence or absence of a vomer as the area is not preserved in either the actual specimen or its cast.
PALATINE
Preservation: Both palatines are preserved in BMNH R.8440 and are complete except for their anteromedial margins.
Contacts: In ventral view the palatine in Mogharemys contacts the maxilla anterolaterally, the other palatine medially on the midline, and the pterygoid posteriorly. In the floor of the fossa orbitalis the palatine also contacts the maxilla anterolaterally and the jugal laterally. A dorsal process of the palatine in the septum orbitotemporale (the posterior wall of the fossa orbitalis), contacts the postorbital dorsally and the frontal dorsomedially. The palatine contacts the ventral margin of the processus inferior parietalis of the parietal.
Structures on dorsal surface: The palatine of Mogharemys forms the medial part of the fossa orbitalis and the floor of the anterior part of the sulcus palatinopterygoideus, as in most other pelomedusids. The foramen palatinum posterius is mostly formed by the palatine and lies in the palatine-pterygoid suture, as in most pleurodires. The posterior extension of the fossa orbitalis past the level of the orbital rim seen in subtribe Stereogenyina is absent in BMNH R.8440.
Structures on ventral surface: The palatine of Mogharemys forms the lateral wall and roof of the choanal passage, but only its more posterior part is preserved. The choanal passage in BMNH R.8440 has a thickened margin along its ventrolateral margin, unlike the thin edge seen in Podocnemis . There is no indication, however, of a secondary palate or even a partial secondary palate. The palatine, however, is thicker and wider in BMNH R.8440 than in taxa outside the subtribe Stereogenyina , and this might bea character in common although we have not used it here due to its variability in turtles in general.
The palatine forms about a third of the triturating surface as preserved in BMNH R.8440. It forms a heavy, deep ridge parallel to the maxillary contact and the accessory ridge on the maxilla. The ridge is deeper than in Dacquemys and Podocnemis .
QUADRATE
Preservation: The posterior moiety of BMNH R.8440 preserves most of the left quadrate, lacking only the anterior part of the cavum tympani. A fragment of the right quadrate is present, adjacent to the basisphenoid and basioccipital contact. The condylus mandibularis in BMNH R.8440 is eroded posterolaterally, but the more medial part of the surface is preserved.
Contacts on lateral surface: No part of the cheek bones or squamosal remain, so none of the lateral surface quadrate contacts can be determined.
Structures on lateral surface: The cavum tympani in Mogharemys is a deep, cone-shaped cavity, as seen in Erymnochelys and Peltocephalus and in contrast to the shallower one in Podocnemis . The incisura columellae auris is enclosed in an oval opening along with the eustachian tube, as in other podocnemidids. The eustachian tube pathway is not separated from the fenestra postotica as in Bairdemys . The antrum postoticum is moderate in size, comparable to that in Podocnemis , smaller than in pelomedusids but larger than in such subtribe Stereogenyina forms as Bairdemys . Although the anterior part of the cavum tympani is missing, enough is preserved to show that the fossa precolumellaris is absent and the area of the cavum here is smooth.
Contacts on dorsal and anterior surface: As in other pleurodires, the quadrate in Mogharemys contacts the prootic anteromedially, the opisthotic posteromedially, the supraoccipital medially, and, presumably although it is absent, the squamosal posteriorly and posterolaterally.
Structures on dorsal and anterior surface: The foramen stapedio-temporale lies on the dorsal surface of the otic chamber formed between the quadrate and prootic as in other podocnemidids.
Contacts on ventral surface: The preserved contacts of the quadrate in Mogharemys are with the basisphenoid medially, the basioccipital posteromedially, and the prootic dorsomedially (not usually visible in the ventral view in a podocnemidid, but the pterygoid is broken away in this specimen).
Structures on ventral surface: The condylus mandibularis in Mogharemys lies just anteri- or to the level of the condylus occipitalis, as in most subtribe Stereogenyina and in contrast to Bairdemys , Podocnemis , Erymnochelys , and Peltocephalus , which have the condylus mandibularis relatively farther anterior.
The cavum pterygoidei in Mogharemys is formed laterally and dorsally by the quadrate as in other podocnemidids, and this is can be seen in BMNH R.8440. The lateral extent of the cavum, however, is much deeper in BMNH R.8440 than in other podocnemidids, such as Podocnemis and Peltocephalus , but it is similar to that in Erymnochelys and Neochelys . Unfortunately, the cavum pterygoidei depth varies too much to use it as a character within the Podocnemididae . In the roof of the cavum pterygoidei is the foramen cavernosum, formed mostly by the prootic but with some quadrate entering into its margin. Just ventromedial to the foramen cavernosum is a much smaller foramen, the foramen nervi facialis, further discussed under Lapparentemys and Pricemys and in the character list.
Contacts on posterior surface: As preserved the quadrate in BMNH R.8440 contacts the opisthotic dorsomedially, the basioccipital ventromedially, the prootic anteromedially, and a very small contact with the exoccipital medially.
Structures on posterior surface: Part of the posterior edge of BMNH R.8440 is eroded, but the fenestra postotica is preserved intact. It is similar to that opening in Erymnochelys , Neochelys , and Peltocephalus in size and shape. There is no separation of the eustachian tube by bone as in some subtribe Stereogenyina . The aditus canalis stapedio-temporalis is large and opens into the nearby canalis stapedio-temporalis. The columella auris of Mogharemys lies in a distinct groove running from the incisura columellae auris to the fenestra ovalis, as in most other podocnemidids. The foramen chorda tympani inferius is probably a small foramen just below the eustachian tube groove.
PTERYGOID
Preservation: The pterygoid is preserved mostly in the anterior moiety of BMNH R.8440. The posterior moiety has a small portion of the suture with the pterygoid along the left edge of the basisphenoid, and there is a fragment of left pterygoid on the medial edge of the condylus occipitalis. The anterior moiety has most of both pterygoids, lacking most of the pterygoid flange and the posterior edge. Some of the left processus trochlearis pterygoidei is damaged.
Contacts on ventral surface: As in other pleurodires the pterygoid of Mogharemys contacts the palatine anteriorly, and the other pterygoid anteromedially. The basisphenoid and quadrate contacts are presumed to have been in the damaged areas.
Structures on ventral surface: The processus trochlearis pterygoidei in Mogharemys lies at right angles to the midline as in most podocnemidids, and has a small, ventrally opening pocket at its base, as seen in Peiropemys and some subtribe Stereogenyina . As in all podocnemidids, BMNH R.8440 has a cavum pterygoidei, but the pterygoid contribution to this is missing and the cavum is open ventrally. The pterygoid flange, usually associated with the cavum, is broken away, but its presence is visible in its base, which is still preserved on both anterior and posterior moieties. The foramen palatinum posterius lies in the palatine-pterygoid suture but is only barely formed by the pterygoid.
Contacts on dorsal surface: In the posterior wall of the septum orbitotemporale in Mogharemys , the pterygoid contacts the postorbital dorsolaterally, the jugal anterolaterally, the palatine anteroventrally, and the parietal anterolaterally, as in the subtribe Stereogenyina , but not as in Podocnemis . The crista pterygoidea is only partially preserved and what is preserved only contacts the parietal.
Structures on dorsal surface: The sulcus palatinopterygoideus is formed in Mogharemys by the pterygoid and palatine ventrally, along with the parietal and postorbital more dorsally. The crista pterygoidea is relatively high in BMNH R.8440, as in the subtribe Stereogenyina , not low as in Podocnemis . It is missing in the area of the foramen nervi trigemini but probably entered its margin based on the remaining bones preserved. The sulcus cavernosus in BMNH R.8440 is wider than in Podocnemis , similar to that in some subtribe Stereogenyina .
SUPRAOCCIPITAL
Preservation: The supraoccipital is preserved only in the posterior moiety of BMNH R.8440. The crista supraoccipitalis is almost completely missing but a short part of its base remains over the foramen magnum.
Contacts: As in other pleurodires the contacts of the supraoccipital in Mogharemys are with the parietal dorsally and anteriorly, the prootic anterolaterally, the opisthotic posterolaterally, and the exoccipital posteroventrally.
Structures: The supraoccipital in Mogharemys is much like that bone in other podocnemidids, and is very similar to that bone in Podocnemis .
EXOCCIPITAL
Preservation: Both exoccipitals are present in the posterior moiety and are complete except for some abrasion on posterior edges.
Contacts: As in other pleurodires, the exoccipital in Mogharemys contacts the supraoccipital dorsally, the opisthotic laterally, and the basioccipital ventrally. It also has a narrow contact with the quadrate ventrolaterally, absent in Podocnemis but present in Cordichelys and Latentemys . We have not used this feature as a character as the contact does vary individually and the presence or absence of the contact is extremely close in some specimens. We feel that larger sample sizes for the recent taxa would be needed to support its use.
Structures: The exoccipital in Mogharemys agrees with the subtribe Stereogenyina in having the two internal foramina nervi hypoglossi join as they leave the skull to form a single, recessed foramen. The condylus occipitalis is damaged, but it can be seen in its base that it is formed by both exoccipitals and the median basioccipital. As in the other podocnemidids the exoccipital closes laterally to form a complete foramen jugulare posterius. The exoccipital forms the medial margin of the fenestra postotica.
BASIOCCIPITAL
Preservation: Although there is some breakage along the posteroventral margin and the condylus occipitalis is incomplete, the basioccipital in BMNH R.8440 is otherwise complete.
Contacts: The basioccipital of Mogharemys contacts the basisphenoid anteriorly, the quadrate laterally, and the exoccipital posterodorsally. Although not entirely clear, there does not seem to be an opisthotic contact.
Structures: The basioccipital forms the median bone in the tripartite condylus occipitalis. The tuberculum basioccipitale is small as in the subtribe Stereogenyina and not protruding as in Podocnemis . There is no concavity on the ventral surface, which is basically flat. The relative length of the basioccipital is intermediate and similar to that in Cordichelys and Latentemys , not very long as in Podocnemis and not very short as in Stereogenys .
PROOTIC
Preservation: Both prootics are present and nearly complete in BMNH R.8440.
Contacts: As in other podocnemidids the prootic in Mogharemys contacts the parietal dorsomedially, the basisphenoid ventrally, the supraoccipital posterodorsally, and the opisthotic posteriorly. There is a presumed contact with the pterygoid anteroventrally, but this is not preserved.
Structures: The prootic of Mogharemys forms the posterodorsal margin of the foramen trigemini, as in most turtles. The other elements forming the foramen are missing in BMNH R.8440 but the remaining morphology suggests that they are the usual suspects, the parietal and pterygoid. Dorsally the prootic forms the medial margin of the foramen stapedio-temporale and the more interior, canalis stapedio-temporalis. The position of these structures in BMNH R.8440 is similar to those in Podocnemis and other podocnemidids.
The prootic of BMNH R.8440 is widely exposed in the cavum pterygoidei and its morphology indicates that Mogharemys has a widely open cavum pterygoidei anteriorly as in Erymnochelys , Peltocephalus , and the Stereogenys / Shweboemys group of the subtribe Stereogenyina (see character list for discussion). The more restricted conditions have a broad or narrow prootic-pterygoid contact in the anterior part of the cavum pterygoidei that extends the canalis cavernosus more anteriorly. In BMNH R.8440 and the other forms, such as Erymnochelys , with a widely open cavum, the prootic and pterygoid do not contact here, and the foramen cavernosum is a foramen in the prootic-quadrate suture, near the foramen nervi facialis.
The fenestra ovale and foramen stapedio-temporale are preserved on both sides but are best seen on the right side of BMNH R.8440. They are similar to those structures in other podocnemidids such as Podocnemis .
OPISTHOTIC
Preservation: The opisthotic is present on both sides of BMNH R.8440, but the posterolateral edges are eroded away on both. The left one is most complete and seems to lack only a small part of the posterolateral end.
Contacts: As in other podocnemidids, the opisthotic in Mogharemys contacts the supraoccipital anteromedially, the prootic anteriorly, the quadrate anterolaterally, and the exoccipital posteromedially. A squamosal contact may or may not have been present.
Structures: The opisthotic of Mogharemys does not appear to enter the edge of the foramen jugulare posterius, which is formed only by the exoccipital. The opisthotic forms the dorsomedial roof of the fenestra postotica. The lateral head vein and stapedial artery apparently extend through the aditus canalis stapedio-temporalis close together and separate anteriorly where the canalis cavernosus lies close to the foramen stapedio-temporale; all presumably related to the large size of the cavum pterygoidei. The processus interfenestralis is covered ventrally by basioccipital and quadrate, and it forms the posterior margin of the fenestra ovalis with the prootic forming the anterior margin, as in all turtles. The opisthotic forms the posterior margin of the foramen jugulare anterius, there is no ossified anterior margin in BMNH R.8440.
BASISPHENOID
Preservation: Most of the basisphenoid is present in BMNH R.8440; the anterior edges, including the rostrum basioccipitale, are eroded away as are the finer structures on the dorsal surface. The condylus occipitalis is also broken.
Contacts on ventral surface: As in the other podocnemidids, the basisphenoid in Mogharemys contacts the pterygoids anterolaterally (contacts represented only by some sutural edges as the pterygoids here are missing), the basioccipital posteriorly, the prootic laterally, and the quadrate laterally, as in the Podocnemididae and Bothremydidae .
Structures on ventral surface: The foramen posterius canalis carotici interni in Mogharemys leads into the foramen anterius canalis carotici interni via a very short canalis caroticus internus, all formed by the basisphenoid. Erymnochelys has a similar arrangement for the canalis, and the canal and foramina are relatively large in size. The cavum pterygoidei is also relatively large in BMNH R.8440, as in Erymnochelys . The basisphenoid forms the ventromedial wall of the cavum, and there is a ventral ridge marking the contact with the pterygoid, now missing.
Contacts on dorsal surface: As in the other podocnemidids, in Mogharemys the contacts of the basisphenoid are with the pterygoid anterolaterally, the prootic dorsally, and the basioccipital posteriorly. As the rostrum basioccipitale is missing (or not ossified), any more possible anterior contacts are not determinable.
Structures on dorsal surface: The rostrum basisphenoidale is probably broken away rather than unossified as the margin is a broken edge. The sella turcica and dorsum sellae are preserved and are similar to Erymnochelys . The sulcus cavernosus is essentially absent as the foramen cavernosum opens in the prootic in the dorsolateral roof of the cavum pterygoidei and the cavum and sulcus cavernosus are not differentiated due to the large size of the cavum pterygoidei. There is no processus clinoideus or foramen nervi abducentis (VI) on either side of the dorsum sellae. The foramen nervi abducentis probably is absent, being included in the large anterior opening of the cavum pterygoidei. The processus clinoideus seems to be broken on both sides.
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