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Grimadelphis spectorum
Taxonomy
Grimadelphis spectorum was named by Godfrey and Lambert (2023). Its type specimen is CMM-V-9941, a partial skull (posterior ros- tral section of the skull, part of the facial region, squamosals, and the occipital condyles), and it is a 3D body fossil. Its type locality is Popes Creek south, Zone 2-3b, which is in a Burdigalian estuary/bay sandstone in the Calvert Formation of Maryland. It is the type species of Grimadelphis.
Synonymy list
| Year | Name and author |
|---|---|
| 2023 | Grimadelphis spectorum Godfrey and Lambert p. 82 figs. Figs. 2.18-2.20 |
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
†Grimadelphis spectorum Godfrey and Lambert 2023
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| S. J. Godfrey and O. Lambert 2023 | Grimadelphis spectorum is a member of Platanidelphidi (sensu Bianucci et al. 2020) because the posterior dorsal infraorbital foramen is more medial than the lateralmost margin of the premaxilla, the dorsal margin of the zy- gomatic process is convex in lateral view, and the ventral margin of the zygomatic process is almost straight. It is a member of Plat- anistidae because of the posterolateral expansion of the premax- illa in the supraorbital region; more complete specimens will be needed to further test anities within platanistid subfamilies. It diers from Araeodelphis, Pomatodelphis, and Zarhachis in the presence of occipital protuberances and from Z. flagellator in not having a hemispherical vertex; in having symmetrical premaxillae in dorsal view anterior to the antorbital notch; in having larger premaxillary foramina positioned farther forward on the rostrum (in Z. flagellator, the premaxillary foramina are at the level of the antorbital notch); in having an occipital shield that is more inclined anteriorly such that the vertex lies at the level, or anterior to a line drawn, in dorsal view, between the anterior margin of the right and left zygomatic processes of the squamosals; in having man- dibular fossae that are much less transversely concave; in having much more deeply incised sternocephalicus fossae; and in having a larger and proportionately anteroposteriorly thicker postglenoid process. It diers from Prepomatodelphis in lacking a bifurcated posterior end of the premaxilla, in having a more laterally directed lateral portion of the nuchal crest (instead of posteriorly directed), and in the zygomatic process being not as deep dorsoventrally in its posterior portion. It diers from P. inaequalis in having sym- metrical premaxillae anterior to the level of the antorbital notch (in P. inaequalis the premaxillae are conspicuously asymmetrical in this region); in having a larger premaxillary foramen; in hav- ing a more dorsoventrally slender and elongate zygomatic process (in P. inaequalis the zygomatic process is very compressed bilater- ally and dorsoventrally deep); in having a less concave mandibu- lar fossa with a proportionately much more robust postglenoid process; in having a much more pronounced and deep sternoce- phalicus fossa; in having an occipital shield that is more inclined anteriorly (in P. inaequalis, the occipital shield is nearly vertical); and, in a palatal view of the skull, in having a forward positioned infraorbital foramen lateral to the positioning of the palatines. It diers from Pomatodelphis bobengi, at least in the posi- tion of the premaxillary foramen (more anterior here) and the anteroposteriorly thicker postglenoid process. It diers from Pomatodelphis santamaria sp. nov. (see below) in having smaller frontals exposed on the vertex, in having a much thinner supraoc- cipital rim that abuts the frontals on the vertex, in having very dif- ferently shaped zygomatic processes and less concave mandibular fossa, in having an occipital shield that is more inclined anteriorly (in P. santamaria sp. nov., the occipital shield, as in Zarhachis and other Pomatodelphis species, is nearly vertical), and in lacking the cylindrical deep fossa/foramen in each exoccipital. It diers from the extant Platanista in, among others, the lack of the bony hood (high maxillary crests) surrounding the melon, the rostrum being transversely wider in its proximal region, its vertex not being as transversely pinched as in Platanista, and its occipital shield being proportionally much broader. |
Measurements
No measurements are available
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| Source: f = family, subo = suborder, o = order | |||||
| References: Nowak 1991, Uhen 2004 | |||||
Age range: Burdigalian or 20.45000 to 15.98000 Ma
Collections: one only
| Time interval | Ma | Country or state | Original ID and collection number |
|---|---|---|---|
| Burdigalian | USA (Maryland) | Grimadelphis spectorum (type locality: 71810) |