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Aegicetus
Taxonomy
Aegicetus was named by Gingerich (2019). Its type is Aegicetus gehennae.
It was assigned to Georgiacetinae by Gingerich (2019).
It was assigned to Georgiacetinae by Gingerich (2019).
Species
A. gehennae (type species)
Synonymy list
| Year | Name and author |
|---|---|
| 2019 | Aegicetus Gingerich p. 5 |
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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.
Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| P. D. Gingerich 2019 | Aegicetus differs from all protocetids for which the cranium is known in hav- ing a relatively narrow cranium with short and downwardly-deflected exoccipital processes on the posterior surface of the braincase (see illustration in Discussion).
Aegicetus differs from Pappocetus [26–29] in being substantially smaller, with cheek teeth about 72–80% as long and a femoral head about 78% in diameter. The metacone on upper P3–4 is much better developed in Aegicetus than in Pappocetus. Aegicetus further differs from Pappo- cetus in lacking fusion of left and right dentaries at the mandibular symphysis. The proximal width of the femur (including the femoral head) is a smaller proportion of femoral shaft width (2.3x compared to 2.9x in Pappocetus). Aegicetus also has a narrower acetabular notch on the innominate. Aegicetus has teeth similar in length and width to those of Babiacetus [30–31], but differs from this genus in having higher-crowned cheek teeth. Aegicetus retains a more distinct meta- cone on P3–4, and retains larger protocone lobes on P3–M3 than are seen in Babiacetus. Aegice- tus further differs from Babiacetus in lacking fusion of left and right dentaries at the mandibular symphysis. Aegicetus is similar to Georgiacetus [2, 32] in size, in retaining an open mandibular symphy- sis, in having a double-rooted P1, and in having relatively long posterior lumbar, sacral, and anterior caudal vertebrae. Aegicetus differs from Georgiacetus in the narrowness of the cranium and in the orientation of the exoccipital processes (see Discussion). Cheek teeth are very simi- lar, but Aegicetus differs in having a lower crowned P2, and an anteroposteriorly narrower pro- tocone lobe on P4. The innominate of Aegicetus differs from that of Georgiacetus in having: (a) a longitudinal spine on the lateral surface of the ilium, which forms the lower border of a dis- tinctive gluteal fossa; (b) a concave anteromedial surface of the ilium possibly related to con- nective-tissue attachment to an auricular process of the sacrum; (c) a more gracile ramus of the ischium; (d) a more robust ramus of the pubis; and (e) an anteroposteriorly shorter and dorsoventrally deeper pubic symphysis. Aegicetus differs from the type specimen of Natchitochia [6], known from 13 associated ver- tebrae and three partial ribs, in being substantially smaller and in lacking the synarthrotic con- nection of the sacrum to the innominates reported for Natchitochia [33]. Aegicetus differs from the referred specimen of Natchitochia in lacking any remnant of pleurapophyseal articu- lation between successive sacral vertebrae [33], and in lacking the expansion and auricular sur- face of the proximal ilium. The proximal width of the femur (including the femoral head) is a smaller proportion of femoral shaft width (2.3x compared to 2.8x in Natchitochia; measure- ments from Fig 7 in Uhen [33]). Aegicetus is similar to Carolinacetus [34] in vertebral size, and both retain an unfused man- dibular symphysis. Aegicetus differs from Carolinacetus in having a narrower cranium (21.4 cm versus about 28.4 cm in width, measured across lateral margins of the exoccipitals) and it differs in the orientation of exoccipital processes (see Discussion). Aegicetus does not have the posterodorsal tongue of the petrosal exposed between the squamosal and exoccipital reported for Carolinacetus. Crenatocetus [25] is based on associated left and right partial dentaries and lower cheek teeth of a late middle Eocene georgiacetine from North Carolina. Judging from comparable lower premolar and molar lengths, Aegicetus is similar in size to Crenatocetus. Aegicetus differs in having a broader P4 (18.3 mm compared to 15.0 mm; a proportional difference of 1.22) and a broader M2 (18.1 mm compared to 12.0; a proportional difference of 1.51). |
Measurements
No measurements are available
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| Source: o = order | |||||
| Reference: Uhen 2004 | |||||
Age range: Priabonian or 37.71000 to 33.90000 Ma
Collections (2 total)
| Time interval | Ma | Country or state | Original ID and collection number |
|---|---|---|---|
| Priabonian | Egypt (Fayum) | A. gehennae (137544) Protocetidae indet. (164491) |