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Janjucetus dullardi
Taxonomy
Janjucetus dullardi was named by Duncan et al. (2025) [Zoobank registration: urn:lsid:zoobank.org:act:E798795F-
0B47-4A8C-B948-E49E4E6BCE5C]. Its type specimen is NMV P256471, a partial skull (partial skull comprising much of the squamosals, periotics, right tympanic bulla, middle ear ossicles, exoccipitals, partial right basioccipital, partial spheno), and it is a 3D body fossil. Its type locality is Jan Juc Beach, which is in a Chattian offshore horizon in the Jan Juc Formation of Australia.
Sister species lacking formal opinion data
Synonymy list
| Year | Name and author |
|---|---|
| 2025 | Janjucetus dullardi Duncan et al. p. 8 |
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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.
†Janjucetus dullardi Duncan et al. 2025
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| R. J. Duncan et al. 2025 | We interpret J. dullardi as a mammalodontid on the basis of: the
presence of an involucral concavity on the medial surface of the tympanic bulla ventral to the involucral ridge; a dorsomedially extended and anteroposteriorly wide crista transversa, which reaches to the level of the rim of the internal acoustic meatus medi- ally (also seen in Salishicetus and Coronodon); and the presence of apicobasal ridges on both the buccal and lingual surfaces of the tooth crowns (also seen in Morawanocetus, Coronodon, and Llanocetus). This specimen shares the following features with J. hunderi to the exclusion of Mammalodon: an obliquely truncated rather than squared anterior margin of the tympanic bulla; an inner posterior prominence of the tympanic bulla mediolaterally broader than the outer posterior prominence at the widest point of the bulla; peri- otic body and posterior process greatly exceed the posterior mar- gin of the fenestra rotunda; anteroposterior and dorsoventral diameters of the anterior process of the periotic are subequal to one another; and the mandibular posterior postcanine teeth lack a distal accessory shelf near the base of the crown. Janjucetus dullardi differs from J. hunderi by possessing the following: the exoccipitals and supramastoid crest contact one another medially and are not separated by a dorsomedial extension of the sternomastoid fossa; a rounded rather than pointed posteromedial corner of the inner posterior prominence of the tympanic bulla; a hiatus Fallopii of the periotic present as an anteriorly directed opening separated dorsally from the rim of the internal acoustic meatus by a thin bridge of bone; lacking an anterior tubercle on the anterior keel of the periotic; a pars cochlearis that is anteroposteriorly longer than dorsoventrally high rather than subequal (as found in both J. hunderi and Mam‑ malodon colliveri); posterior upper cheek teeth with two large, subequal distal denticles rather than three; and the posterior cheek teeth possess a pronounced lingual ridge with lingually projecting denticles. This specimen also differs further from Mammalodon colliveri by: lacking nodule-like transverse creases on the anterior half of the involucrum; having a suprameatal fossa and a superior process that runs from a pointed anterior spike to a pronounced postero- dorsal angle continuous with the vestibular aqueduct; lacking a pronounced caudal tympanic process; lacking a dorsomedial angle of the periotic; having a shallow stylomastoid fossa posterodorsal to the stapedial muscle fossa; having proximal opening of facial canal less than half the size of the internal acoustic meatus; and the vestibular aqueduct being a single opening. We note, however, that these characters cannot be assessed for the holotype of J. hunderi. |
Measurements
No measurements are available
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| Source: subo = suborder, o = order | |||||
| Reference: Uhen 2004 | |||||