Latentemys, 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-FF09-5EE3-FEFB-A0DC9C70D69B |
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treatment provided by |
Felipe |
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scientific name |
Latentemys |
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Latentemys Figures 58–61 View Fig View Fig View Fig View Fig
PREFRONTAL
Preservation: The anterior margins of both prefrontals in BMNH R.11998 are broken edges.
Contacts: As in Bairdemys venezuelensis .
Structures: The prefrontal in Latentemys is flat, not convex as in Bairdemys venezuelensis . There is no midline depression as in Cordichelys .
FRONTAL
Preservation: Both frontals are complete in BMNH R.11998.
Contacts: As in Bairdemys venezuelensis : the frontal on the midline, the prefrontal anteriorly, the postorbital posterolaterally, the parietal posteriorly, and on the ventral surface, the palatine posteroventrally.
Structures: The frontal in Latentemys borders the orbit as in Bairdemys venezuelensis , and it sends a process posteroventrally to contact the dorsal process of the palatine, also as in other subtribe Stereogenyina .
PARIETAL
Preservation: The parietals in BMNH R.11998 are missing all the dorsal plates except those directly over the cavum cranii. None of the original posterior or lateral margins are preserved.
Contacts and structures of dorsal plate: As preserved, the only contacts in BMNH R.11998 are with the other parietal medially, the frontal anteriorly, and the postorbital anterolaterally.
Contacts and structures of processus inferior parietalis: The anterior margin of the processus is broken away in BMNH R.11998, but what is present agrees with Brontochelys . It contacts the palatine anteroventrally, the pterygoid ventrally, the prootic posteroventrally, and the supraoccipital posteriorly. As in other podocnemidids, the foramen nervi trigemini in Latentemys is formed by the parietal, prootic and pterygoid.
JUGAL
Preservation: On the left side of BMNH R.11998 the jugal is complete internally and is missing only the posterior part of the lateral plate externally. The right jugal lacks the lateral plate and the dorsal part of the medial process.
Contacts and structures of lateral plate: As preserved, the jugal in Latentemys contacts the maxilla anteroventrally and the postorbital dorsally. The jugal forms the posteroventral part of the orbital rim, as in the other subtribe Stereogenyina .
Contacts of medial process: In the anterior wall of the septum orbitotemporale and the floor of the fossa orbitalis, the jugal contacts the maxilla anteriorly and laterally, the palatine medially, and the postorbital posterodorsally, as in Cordichelys . In the septum orbitotemporale posterior wall, the jugal contacts the postorbital dorsomedially, the palatine ventromedially, and the pterygoid posteriorly in a relatively short suture.
Structures of medial process: The medial process of the jugal in Latentemys does not reach the triturating surface, and it forms the ventral portion of the septum orbitotemporale, as in most of the other subtribe Stereogenyina .
QUADRATOJUGAL
The quadratojugal is not preserved in BMNH R.11998.
SQUAMOSAL
Preservation: The squamosal in BMNH R.11998 is preserved on both sides, but only the conical posterior part is present, and the anterior contacts with cheek elements is missing.
Contacts and structures: As in other subtribe Stereogenyina , the squamosal in Latentemys contacts the quadrate anteromedially and the opisthotic medially. As in other subtribe Stereogenyina , the squamosal is a cone-shaped bone fitting around antrum postoticum of quadrate. It is similar to that bone in Bairdemys , but lacks the ventral flange seen in that taxon, agreeing with Cordichelys .
POSTORBITAL
Preservation: The postorbital is preserved on both sides of BMNH R.11998. On the right side only the most medial part of the medial process is preserved in the orbit, on the left side all of the medial part and some of the lateral plate is preserved, but the posterior part of the lateral plate is missing.
Contacts and structures of lateral plate: As preserved, the postorbital in Latentemys contacts the frontal anteromedially and the jugal ventrally. It forms the posterodorsal part of the orbital rim.
Contacts of medial process: In the anterior surface of the septum orbitotemporale the postorbital of Latentemys contacts the frontal dorsomedially, the palatine ventrally, and the jugal ventrolaterally. In the posterior surface of the septum orbitotemporale, the postorbital contacts the parietal dorsomedially, the pterygoid ventromedially, and the jugal ventrolaterally.
Structures of medial process: The postorbital forms the dorsal part of the septum orbitotemporale and part of the roof and lateral wall of the sulcus palatinopterygoideus.
PREMAXILLA
The premaxilla is not preserved in BMNH R.11998.
[C. Wilson, del.]
MAXILLA
Preservation: Both maxillae are preserved in BMNH R.11998. Both appear to be complete. They may lack a small portion along the premaxilla contact.
Contacts of vertical plate: As in Bairdemys venezuelensis , except for the premaxilla contact, which is unknown.
Structures of vertical plate: The part of the orbital margin and choanal passages formed by the maxilla in Latentemys is very similar to those areas in Cordichelys .
Contacts of horizontal plate: As preserved, the maxilla in Latentemys contacts the palatine posteromedially and the jugal posterolaterally.
Structures of horizontal plate: The labial ridge is high and narrow as in Bairdemys . The large ventral convexity characteristic of Bairdemys venezuelensis is represented in Latentemys by a shallow convexity as in Cordichelys .
PALATINE Preservation: The palatine in Latentemys is preserved in BMNH R.11998 on both sides.
Both are missing most of the posterior contact with the pterygoids and the left one has some of the anteromedial edge broken.
Contacts: As in Bairdemys venezuelensis , on the ventral surface the palatine in Latentemys contacts the maxilla anterolaterally, the other palatine medially on midline above the secondary palate, and the pterygoid posteriorly. On the dorsal surface the palatine contacts the frontal anterodorsally. In the fossa orbitalis, the palatine contacts the maxilla anterolaterally, the jugal laterally, the postorbital posterolaterally, and the frontal dorsomedially.
Structures on dorsal surface: The palatine in Latentemys forms much of the floor of the fossa orbitalis, the posteroventral margin of the foramen orbito-nasale, and the anterior floor of sulcus palatinopterygoideus. The foramen palatinum posterius could possibly be a small hole just under the posterior end of the secondary palate, near the pterygoid suture.
Structures on ventral surface: The palatine in Latentemys forms less than half of the posterior triturating surface secondary palate, in contrast to Bairdemys venezuelensis in which the palatine forms at least half of the palate and is wider than in Latentemys . The medial edge of the median cleft in Latentemys is curved as in Bairdemys and Cordichelys .
QUADRATE
Preservation: The quadrates in BMNH R.11998 lack their anterior cheek portions and the anterior part of the cavum tympani, but the medial and ventral portions are present on both sides.
Contacts on lateral surface: As preserved, the only contact is with the squamosal posterodorsally.
Structures on lateral surface: The posterior portion of the cavum tympani in Latentemys shows a closed incisura columellae auris containing stapes and eustachian tube that is separated posteriorly from the fenestra postotica as in Bairdemys but in contrast to the other subtribe Stereogenyina . The fossa precolumellaris is not preserved. The antrum postoticum in Latentemys is small, as in Cordichelys , but not flattened and nearly absent as in Bairdemys .
Contacts and structures on dorsal and anterior surface: As in Bairdemys venezuelensis and Cordichelys .
Contacts on ventral surface: Most of the contacts in Latentemys are as in Bairdemys , with the basisphenoid medially, the basioccipital posteromedially, and the prootic medially, within the cavum pterygoidei. But the cavum pterygoidei in Latentemys is comparatively larger than in most of the other subtribe Stereogenyina , so that the pterygoid and quadrate are separated medially by the basisphenoid, although they contact on the lateral side of the cavum pterygoidei.
Structures on ventral surface: The condylus mandibularis in Latentemys is in about the same relative position as it is in Bairdemys venezuelensis . The cavum pterygoidei in Latentemys is also similar in position and orientation to that in Cordichelys , but relatively larger. Both quadrates show the opening of the cavum cavernosus, formed between the quadrate, pterygoid, and prootic.
Contacts on posterior surface: As in Bairdemys venezuelensis .
Structures on posterior surface: The fenestra postotica in Latentemys is separated by bone from the sulcus eustachii, in contrast to all other subtribe Stereogenyina , except Bairdemys .
PTERYGOID
Preservation: Both pterygoids in BMNH R.11998 are present but damaged to some extent. The anterior margins of both are broken edges except on the left side. The right processus trochlearis pterygoidei and both pterygoid flanges are missing and the posterior floor of the cavum pterygoidei is broken away on both sides.
Contacts on ventral surface: The contacts are with the palatine anteriorly, the basisphenoid posteromedially, and the quadrate posterolaterally. The midline contact with the other pterygoid is long in Latentemys , longer than in Bairdemys and Cordichelys .
Structures on ventral surface: The left processus trochlearis pterygoidei is present in BMNH R.11998 and is at right angles to the midline as in other subtribe Stereogenyina . There is a small concavity on the ventral side of the base of the processus in Latentemys , as in other subtribe Stereogenyina . The cavum pterygoidei is mostly visible due to the breakage of some of the pterygoid that floors it. The foramen cavernosum lies in the dorsal roof of the cavum pterygoidei as in other subtribe Stereogenyina and is formed laterally by the pterygoid. The prootic appears to form its anterior margin and the quadrate its medial margin, as in Cordichelys . The pterygoid flange is broken away including its base on the right side, but some of the base remains on the left.
Contacts and structures on dorsal surface: On the posterior surface of the septum orbitotemporale in Latentemys , the pterygoid contacts the postorbital anterodorsally, the jugal anteroventrally, the palatine ventrally, and the parietal anterodorsally. Most of the crista pterygoidea is broken away in BMNH R.11998, the contacts with the parietal dorsally and the prootic posterodorsally are preserved. The sulcus palatinopterygoideus is formed by the pterygoid laterally, but most of that structure is broken away in BMNH R.11998. The foramen nervi trigemini is formed by the usual elements in Latentemys , the pterygoid ventrally, the parietal anterodorsally, and the prootic posterodorsally. On both sides the pterygoid forms what appears to be the foramen nervi vidiani just lateral to the rostrum basisphenoidale and in the floor of the sulcus cavernosus.
SUPRAOCCIPITAL
Preservation: In BMNH R.11998 all but the anterior part of the supraoccipital is broken away.
Contacts and structures: As in Bairdemys venezuelensis and other subtribe Stereogenyina , the supraoccipital in Latentemys contacts the parietal dorsally and anteriorly, the prootic anterolaterally, the opisthotic posterolaterally, and the exoccipital posteroventrally. The crista supraoccipitalis is not preserved.
EXOCCIPITAL
Preservation: In BMNH R.11998 both exoccipitals are present and complete.
Contacts: As in Bairdemys venezuelensis .
Structures: The condylus occipitalis in Latentemys is broken but appears to have been formed by both exoccipitals and the basioccipital. The foramen nervi hypoglossi is recessed and the two foramina medially join to form one distally. The foramen jugulare posterius is closed and separated from the fenestra postotica by a relatively long exoccipital contact (with itself, as is usually the case in turtles, oddly enough).
BASIOCCIPITAL
Preservation: In BMNH R.11998 the basioccipital is complete except for a small part of the condylus occipitalis.
Contacts and structures: As in Cordichelys .
PROOTIC
Preservation: In BMNH R.11998 both prootics are present and complete. They are both free of matrix and visible internally as well as externally.
Contacts and structures: As in Cordichelys .
OPISTHOTIC
Preservation: In BMNH R.11998 both opisthotics are present and complete except for some erosion on the distalmost edges.
Contacts and structures: As in Cordichelys and Bairdemys venezuelensis and B. hartsteini .
BASISPHENOID
Preservation: In BMNH R.11998 the basisphenoid is complete and free of matrix internally and externally.
Contacts on ventral surface: The basisphenoid in Latentemys contacts the pterygoids anterolaterally, the basioccipital posteriorly, the prootic dorsally inside the cavum pterygoidei, and the quadrate laterally.
Structures on ventral surface: The basisphenoid in Latentemys forms the lateral walls to the cavum pterygoidei and, anteriorly, the foramen posterius canalis carotici interni that leads, by means of a short canalis caroticus internus, to the foramen anterius canalis carotici interni. The cavum pterygoidei in Latentemys is relatively larger than in other subtribe Stereogenyina , not by means of an extension laterally into the quadrate as in Mogharemys , but by having a larger diameter. The basisphenoid in Latentemys is relatively short in comparison to Bairdemys and Cordichelys , so that there is a long pterygoid contact anteriorly.
Contacts on dorsal surface: The dorsal contacts in Latentemys , not usually seen, are with the pterygoid anterolaterally, the prootic laterally, presumably with some part of the palatines anteriorly, but not preserved in BMNH R.11998, and the basioccipital posteriorly.
Structures on dorsal surface: The rostrum basisphenoidale in Latentemys is a solid rod with the trabeculae fused but not extending anteriorly, defining the sella turcica posteriorly and medially between the paired trabeculae. The rostrum basisphenoidale in Latentemys is shorter than in Brontochelys , Peltocephalus , Erymnochelys , and Podocnemis . There is the usual sulcus cavernosus lateral to the trabeculae defining the sella turcica, but as the foramen cavernosum is in the dorsal roof of the cavum pterygoidei, it is not clear what the path of the lateral head vein would be.
The dorsum sellae in Latentemys is a prominent, overhanging shelf, lying over the posterior end of the sella turcica, in contrast to the very low dorsum seen in Brontochelys . The foramen anterius canalis carotici interni lies at each posterolateral end of the sella turcica beneath the dorsum sellae, as in most Podocnemis , but in contrast to Brontochelys in which the low dorsum exposes the foramen anterius canalis carotici interni dorsally. The paired processus clinoideus may have been present premortem but the position is now a broken surface. The position of the foramen nervi abducentis (VI) is not clear.
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