Brontochelys, Gaffney & Meylan & Wood & Simons & De Almeida Campos, 2011
|
publication ID |
https://doi.org/ 10.1206/350.1 |
|
persistent identifier |
https://treatment.plazi.org/id/C95DDC2B-FF16-5EEC-FEE4-A2F09C2DD629 |
|
treatment provided by |
Felipe |
|
scientific name |
Brontochelys |
| status |
|
Brontochelys Figures 62–66 View Fig View Fig View Fig View Fig
PREFRONTAL
Preservation: The snout of BMNH R.8570 is eroded and damaged to some extent, so only part of the right prefrontal is preserved.
Contacts: As preserved, the prefrontal of BMNH R.8570 contacts the maxilla anteroventrally and the frontal posteriorly.
Structures: The prefrontal in BMNH R.8570 forms the anterodorsal margin of the orbit, which in Brontochelys faces forward to an unusual degree compared with other subtribe Stereogenyina . There appears to be no remaining natural margins of the apertura narium externa. There may have been a prefrontal anterior extension as seen in Bairdemys , as this area is damaged in most of the subtribe Stereogenyina specimens. None of the subtribe Stereogenyina taxa have a broad ventral process of the prefrontal, so the narrow nature of it in BMNH R.8570 is probably accurate.
FRONTAL Preservation: Both frontals are present and complete except for their anterior areas. The left one has a broken margin from the midline to its contact with the postorbital and the right one, although more complete and retaining its prefrontal contact, also has breakage along the orbital margin. The internal areas seem intact.
Contacts: In dorsal view the frontal in BMNH R.8570 contacts the other frontal on the midline, the prefrontal anteriorly, the postorbital posterolaterally, and the parietal posteriorly. On its ventral surface the frontal also contacts the dorsal process of the palatine along the medial edge of the septum orbitotemporale, as in other subtribe Stereogenyina .
Structures: The frontal forms the dorsal edge of the orbital margin as in the other subtribe Stereogenyina . The orbital margins are damaged in BMNH R.8570, but it seems likely that their orientation is correct. They were probably increased in size due to postmortem damage. On the ventral surface the frontal sends a stout process ventrally to meet the dorsal process of the palatine, forming the medial edge for the septum orbitotemporale, as in the other subtribe Stereogenyina . The space between the two frontal-palatine contacts is wider in Brontochelys than in Lemurchelys , Cordichelys and Latentemys , and probably Stereogenys (based on the endocast).
PARIETAL
Preservation: The parietals in BMNH R.8570 lack all the skull roofing portions, the area directly over the braincase is preserved and the internal parietal areas are preserved.
Contacts and structures of dorsal plate: As preserved, the parietal in Brontochelys contacts the frontal anteriorly, the other parietal medially, and the postorbital anterolaterally. None of the skull roof overlying the fossa temporalis remains.
Contacts and structures of processus inferior parietalis: The parietal in Brontochelys contacts the frontal ventral process anteriorly, the pterygoid ventrally, the prootic posteroventrally, and the supraoccipital posteriorly. There does not seem to be a palatine contact. Lateral to the processus inferior parietalis in pleurodires is the septum orbitotemporale, which has the parietal forming the roof anterodorsally and the lateral wall. The foramen nervi trigemini in Brontochelys is formed by the parietal anterodorsally, the prootic dorsolaterally, and, probably, the pterygoid ventrally, although the latter is broken away on both sides.
Septum orbitotemporale: The ventral surface of the frontal in Brontochelys and other Stereogenyini is dominated by a thick and well-developed parasagittal ridge, the septum orbitotemporale, separating the fossa orbitalis laterally from the sulcus olfactorius medially. This ridge is lowest anteriorly, where it is a continuation of the ridge on the ventral surface of the prefrontal that separates the fossa orbitalis and the fossa nasalis. The ridge on the frontal thickens and deepens posteriorly, where it contacts the processus inferior parietalis posteromedially and the posterior wall of the fossa orbitalis posterolaterally.
JUGAL
Preservation: The jugal on both sides of BMNH R.8570 retains the medial process and the orbital part of the lateral plate, but the cheek areas are missing and some of the surface has been eroded on both sides.
Contacts and structures of lateral plate: The contacts preserved in Brontochelys are with the maxilla anteroventrally, and the postorbital dorsally. There is no indication of the extent of the cheek bones. The jugal forms the ventrolateral part of the orbital rim.
Contacts and structures of medial process: In the orbital floor, the jugal in Brontochelys contacts the maxilla anteriorly and laterally and the palatine medially. In the septum orbitotemporale (posterior view), the jugal contacts the postorbital dorsomedially, the palatine ventromedially, the pterygoid posteriorly, and the maxilla ventrally, all as in such subtribe Stereogenyina as Latentemys . Also as in other subtribe Stereogenyina , the jugal does not form part of the triturating surface.
QUADRATOJUGAL
The quadratojugal is not preserved in BMNH R.8570.
SQUAMOSAL
The squamosal is not preserved in BMNH R.8570.
POSTORBITAL Preservation: The postorbital in BMNH R.8570 lacks the lateral plate on both sides, but the medial process is present on both sides.
Contacts and structures of lateral plate: In Brontochelys the contacts are with the frontal anteromedially, the jugal ventrally, and the parietal posteromedially. The postorbital forms the posterodorsal rim of the orbit as in the other subtribe Stereogenyina .
Contacts of medial process: In the anterior view of the septum orbitotemporale the postorbital contacts the frontal dorsomedially, the palatine ventromedially, and the jugal ventrally. In posterior view of the septum orbitotemporale the postorbital contacts the parietal dorsomedially, the pterygoid ventromedially, and the jugal ventrolaterally.
Structures of medial process: The postorbital of Brontochelys participates in the formation of the septum orbitotemporale.
PREMAXILLA
The premaxilla is not preserved in BMNH R.8570.
MAXILLA
Preservation: Most of both maxillae are preserved in BMNH R.8570, but the anterior sutural contacts with the premaxillae are damaged and lack sutural surfaces, so the anteromedial extent of the maxilla is unknown. However, the close similarity with other subtribe Stereogenyina suggests that little of either maxilla is missing. Similarly, the posterior edge of the maxilla on each side is a broken surface with no indication of a sutural contact.
Contacts and structures of vertical plate: As preserved, the maxilla in Brontochelys contacts only the prefrontal anterodorsally and the jugal posterodorsally. The maxilla forms the ventral margin of the orbital rim. There is no remnant of the cheek formation. The orbital rim in Brontochelys defines an opening that faces more anteriorly than laterally, as in all subtribe Stereogenyina , but in Brontochelys the orbit faces even more anteriorly than in Latentemys , Cordichelys , Shweboemys , and Stereogenys . It is about the same as in Bairdemys venezuelensis and Lemurchelys . The maxilla shape reflects the snout shape and Brontochelys has an unusually broad snout.
Contacts of horizontal plate: The maxilla as preserved in Brontochelys contacts the jugal posterolaterally and the palatine posteriorly.
Structures of horizontal plate: The maxilla makes up the anterior half of the secondary palate in BMNH R.8570, as in the other subtribe Stereogenyina . It forms the choanal passage that divides the internal nares from the braincase proper. There is a large foramen orbitonasale communicating between the choanal passage and the fossa orbitalis as in the other subtribe Stereogenyina . The median opening that divides the secondary palate has no anterior margin because the premaxillae are missing. The median opening is curved on both sides in Brontochelys as in Latentemys , but in contrast to Stereogenys in which the median opening is parallel.
VOMER
There is no indication that a vomer was present in Brontochelys .
PALATINE
Preservation: Both palatines are preserved in BMNH R.8570. They lack some of the thin bone on the dorsal roof of the choanal passages and the medial margins have a few breaks, but otherwise they are complete.
Contacts: As in the other subtribe Stereogenyina the palatine in Brontochelys contacts the maxilla anteriorly, the other palatine medially on midline above the secondary palate, and the pterygoid posteriorly. On the dorsal surface the palatine contacts a robust ventral process from the frontal and the anterior part of the processus inferior parietalis.
Structures on dorsal surface: The palatine in Brontochelys makes up a major part of the fossa orbitalis floor, as in other subtribe Stereogenyina , and the dorsal process forms the ventromedial edge of the septum orbitotemporale. In the subtribe Stereogenyina the fossa orbitalis has a posterior concavity that is greater than in other podocnemidids. In Brontochelys the fossa orbitalis concavity is shallower than in the other subtribe Stereogenyina , even though the fossa itself is relatively larger. The dorsal palatine process in Brontochelys does not reach the parietal as in Shweboemys and Stereogenys .
Structures on ventral surface: The palatine forms the posterior half of the secondary palate in Brontochelys , and the posterior margin of the apertura narium interna. The choanal passage that connects the apertura narium externa with the apertura narium interna is formed posteriorly by the palatine. The palatine forms not only the primary palate but the secondary one as well. In Brontochelys the medial margin is curved as in Bairdemys . There is no large foramen palatinum posterius in the subtribe Stereogenyina as in other pleurodires, but a small foramen in BMNH R.8570 is in the right place and on both sides, and may be this foramen.
QUADRATE
Preservation: In BMNH R.8570 the only parts of the quadrate remaining are small medial portions attached to the otic chambers. All of the cavum cranii and lateral portions are missing. On the right side the quadrate below the fenestra postotica remains and on the left side a small part next to the basisphenoid remains.
Contacts and structures: The only contacts remaining in Brontochelys are with the basisphenoid medially and the basioccipital posteromedially. The quadrate forms part of the medial wall of the cavum ptergoidei on the right side and the floor of the groove leading from the incisura columellae auris to the fenestra ovalis, as in other subtribe Stereogenyina .
PTERYGOID
Preservation: Both pterygoids in BMNH R.8570 are preserved, but lack the pterygoid flanges and thin bone around the cavum pterygoidei on both sides. The left cavum is filled with matrix; the right one is open laterally. The lateral edges of the processus trochlearis pterygoidei are abraded as well.
Contacts on ventral surface: As in the other subtribe Stereogenyina the pterygoid in Brontochelys contacts the palatine anteriorly, the other pterygoid anteromedially, the basisphenoid posteromedially, and the quadrate posterolaterally.
Structures on ventral surface: The processus trochlearis pterygoidei in Brontochelys lies at approximately a right angle to the midline, as in other subtribe Stereogenyina . The cavum pterygoidei is filled with matrix on the left side but broken open on the right. It is formed as in other subtribe Stereogenyina by the pterygoid ventrally, the quadrate posterolaterally, the basisphenoid medially, and the prootic anterolaterally. It is relatively large as in other subtribe Stereogenyina , such as Bairdemys and Latentemys . The anterior wall of the cavum pterygoidei is open also as in other subtribe Stereogenyina as well as Erymnochelys and Peltocephalus . On the right side of BMNH R.8570 the foramen cavernosum can be seen in the roof of the cavum cavernosum, indicating the absence of the anterior wall of the cavum. The very short canalis cavernosum and the nearby entry into it can also be seen here. Although the pterygoid flange is not preserved, its base is present on both sides of BMNH R.8570 and it has the full extent seen in other podocnemidids.
Contacts on dorsal surface: In the posterior wall of the septum orbitotemporale in Brontochelys the pterygoid contacts the palatine ventrally, the jugal anterolaterally, the postorbital dorsolaterally, and the parietal anterodorsally. The parietal contact is relatively wide in comparison to the contact in Podocnemis . In the crista pterygoidea the pterygoid contacts the parietal anterodorsally, the prootic posterodorsally. Anteriorly on the dorsal surface the pterygoid contacts the palatine anteriorly and the basisphenoid medially.
Structures on dorsal surface: The foramen nervi trigemini in Brontochelys has its anterior edge damaged, but it was formed by the pterygoid ventrally, the parietal anterodorsally, and the prootic posterodorsally. The sulcus palatinopterygoideus in Brontochelys and the other subtribe Stereogenyina is a large tunnel with thick bone laterally. Its floor is formed by the pterygoid posteriorly and the palatine anteriorly.
SUPRAOCCIPITAL
Preservation: The ventral portion of the supraoccipital is complete in BMNH R.8570, but the dorsal portion, the crista supraoccipitalis, is broken away for its entire length.
Contacts: As in the other podocnemidids the supraoccipital in Brontochelys contacts the parietal anterodorsally, the prootic anterolaterally, the opisthotic posterolaterally, and the exoccipital posteroventrally.
Structures: The crista supraoccipitalis extended at least to the foramen magnum.
EXOCCIPITAL
Preservation: Both exoccipitals are preserved in BMNH R.8570. They are both somewhat eroded along their posterolateral edges, but otherwise seem complete. The sutures in some areas are indistinct.
Contacts: The exoccipital of Brontochelys has the usual contacts with the supraoccipital dorsally, the opisthotic laterally, the quadrate ventrolaterally, and the basioccipital ventrally.
Structures: The condylus occipitalis is broken distally in BMNH R.8570, but the two exoccipitals and the basioccipital can be seen in the preserved base. The foramina nervi hypoglossi leave the skull in two foramina, but the exit is united as one recessed foramen, as in nearly all other subtribe Stereogenyina . The foramen jugulare posterius is closed completely by the exoccipital.
BASIOCCIPITAL
Preservation: The basioccipital in BMNH R.8570 has some erosion along its lateral margins and some of the contacts are unclear.
Contacts: As in other subtribe Stereogenyina the basioccipital in BMNH R.8570 contacts the basisphenoid anteriorly, the quadrate laterally, the exoccipital posterodorsally, and the opisthotic dorsolaterally.
Structures: The basioccipital in Brontochelys is relatively short, shorter than in Bairdemys venezuelensis , but not as short as in its near relatives, Stereogenys and Shweboemys .
PROOTIC
Preservation: Both prootics are preserved in BMNH R.8570, the right one is complete and the left one has some damage around the lateral contact with the pterygoid in the wall of the cavum pterygoidei.
Contacts: As in the other subtribe Stereogenyina , the prootic contacts in BMNH R.8570 are with the parietal anterodorsally, the quadrate laterally, the supraoccipital dorsally, the basisphenoid ventromedially (on the medial side of the cavum pterygoidei), the pterygoid ventrolaterally (on the lateral side of the cavum pterygoidei), and the opisthotic posteriorly.
Structures: The foramen nervi trigemini in Brontochelys is formed by the prootic posterodorsally, the parietal anterodorsally, and the pterygoid ventrally, as in other podocnemidids. The foramen stapedio-temporale is formed by the prootic medially and the quadrate laterally, as in most turtles. As in other subtribe Stereogenyina as well as in Mogharemys and Erymnochelys , the foramen cavernosum lies in the roof of the cavum pterygoidei formed by the quadrate and prootic. The prootic forms the anterior margin of the hiatus acusticus, visible in BMNH R.8570. Just anterior to it the fossa acustico-facialis contains the more ventral foramen nervi facialis (VII) and the more dorsal foramen nervi acustici (VIII).
OPISTHOTIC
Preservation: Both opisthotics are present in BMNH R.8570 and both lack their distal ends.
Contacts: As in other podocnemidids the opisthotic of Brontochelys contacts the supraoccipital anteromedially, the prootic anteriorly, the quadrate laterally, and the exoccipital posteromedially. The squamosal is not preserved, so that possible contact is indeterminate.
Structures: The opisthotic in Brontochelys forms the roof and medial wall for the fenestra postotica. The lateral wall of the fenestra postotica is not preserved.
BASISPHENOID
Preservation: The basisphenoid in BMNH R.8570 is nearly complete.
Contacts on ventral surface: The basisphenoid in Brontochelys contacts the pterygoid anterolaterally, the basioccipital posteriorly, and the quadrate laterally.
Structures on ventral surface: The basisphenoid forms the medial wall and part of the floor and roof of the cavum pterygoidei. Brontochelys has the anteriorly open condition of the cavum, and the basisphenoid has the foramen posterius canalis carotici interni in its lateral surface. This surface is somewhat concave as well, due to the large size of the cavum pterygoidei.
The basisphenoid in Brontochelys is wider than the basioccipital in contrast to all other subtribe Stereogenyina in which it is the same or narrower.
Contacts on dorsal surface: The basisphenoid of Brontochelys contacts the pterygoid anterolaterally, the prootic laterally, the palatine anteriorly, and the basioccipital posteriorly, as in other podocnemidids.
Structures on dorsal surface: Brontochelys has a low, not overhanging, dorsum sellae, a shallow sella turcica, and a long but low rostrum basisphenoidale, in contrast to the higher dorsum sellae, deeper sella turcica, and more sharply defined rostrum basisphenoidale of Latentemys . The sulcus cavernosus in Brontochelys is a relatively wide groove confluent with the cavum pterygoidei, as in the rest of the taxa with an anteriorly open cavum. The foramen anterius canalis carotici interni is in the lateral edge of the shallow sella turcica and opens directly anteriorly from the short canalis caroticus internus. There is no apparent processus clinoideus.
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.