Protocetus

{{speciesbox

| name = Protocetus

| image = Protocetus.jpg

| image_upright = 0.8

| image_caption = Underside of a skull cast at the Museum für Naturkunde, Berlin

| fossil_range = Middle Eocene, {{Fossil range|45|43.5}}

| genus = Protocetus

| parent_authority = {{Harvnb|Fraas|1904}}

| species = atavus

| authority = {{Harvnb|Fraas|1904}}

}}

Protocetus atavus ("first whale") is an extinct species of primitive cetacean from Egypt. It lived during the middle Eocene period 45 million years ago. The first discovered protocetid, Protocetus atavus was described by {{Harvnb|Fraas|1904}} based on a cranium and a number of associated vertebrae and ribs found in middle Lutetian Tethyan marine limestone from the Mokattam Formation at Gebel Mokattam near Cairo, Egypt.{{Harvnb|Bianucci|Gingerich|2011|p=1174}}

Description

Image:Protocetus size.png

Protocetus are believed to have had a streamlined, whale-like body around {{convert|2.5|m|ft}} long, but was probably primitive in some respects.Palmer D (ed.) (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 230. {{ISBN|978-1-84028-152-1}}.

Many protocetids (like Maiacetus, Rodhocetus) possessed well developed innominates and hind limbs, often attached to the backbone with a sacrum. Protocetus are known to have had at least one sacral vertebrate,Gingerich P.D. (2010). "Cetacea". In Werdelin L & Sanders W.J. (eds.). Cenozoic mammals of africa. Berkeley: University of California Press, p. 873–899 and likely possessed hind limbs and webbed toes. Despite previous proposals to the contrary, the current general consensus is that Protocetus and other protocetids lacked tail flukes.Thewissen, J.G.M., Cooper, L.N., George, J.C. et al. "From Land to Water: the Origin of Whales, Dolphins, and Porpoises." Evo Edu Outreach 2 (1): p. 272–288 (2009)

The head of Protocetus measured about 0.6 meters long.Gingerich, Philip D.; Arif, Muhammad; Clyde, William C. (1995). "New Archaeocetes (Mammalia, Cetacea) from the middle Eocene Domanda Formation of the Sulaiman Range, Punjab (Pakistan)". Contributions from Museum of Paleontology, the University of Michigan. 29 (11): p. 291–330 The jaws were long and lined with sharp teeth. While it did not have a true blowhole, the nostrils were placed further back on the head than in most land mammals. Unlike the more primitive Pakicetus, the structure of the ears suggests that Protocetus was able to hear properly underwater, although it is unlikely that it could echolocate. Similarly, it retained sufficient olfactory apparatus to have a good sense of smell, although it probably relied more on its eyesight to find prey.

=Skull=

Recent high-resolution CT scans of the holotype skull of Protocetus atavus (SMNS-P-11084) have provided the first detailed reconstruction of its endocranial anatomy, offering significant insights into the evolution of sensory systems in early cetaceans.{{Cite journal|last1=Berger |first1=E. |last2=Amson |first2=E. |last3=Peri |first3=E. |last4=Gohar |first4=A. S. |last5=Sallam |first5=H. M. |last6=Ferreira |first6=G. S. |last7=Chowdhury |first7=R. R. |last8=Martinez |first8=Q. |title=The endocranial anatomy of protocetids and its implications for early whale evolution |year=2025 |journal=Evolution |doi=10.1093/evolut/qpaf109 |pmid=40372400 |doi-access=free }} The study revealed that Protocetus had a relatively high encephalization quotient (EQ) compared to other middle Eocene cetaceans such as Rodhocetus and Remingtonocetus, suggesting an earlier onset of brain enlargement than previously assumed in whale evolution. Notably, the olfactory bulbs and tracts were well-developed, comprising up to 3.8% of the endocast volume, a value comparable to that of some terrestrial mammals. The anatomy of the nasal cavity, including the dorsal nasal meatus and vomeronasal groove, further supports the interpretation that Protocetus retained functional airborne olfaction. These findings challenge the long-held view that olfactory capabilities regressed early in cetacean evolution and suggest that the reduction of olfactory structures may have occurred later, potentially only after the emergence of fully aquatic forms like basilosaurids.{{cite web |last1=Berger |first1=Elena |last2=Amson |first2=Eli |last3=Peri |first3=Emanuele |last4=Gohar |first4=Abdullah S. |last5=Sallam |first5=Hesham M. |last6=Ferreira |first6=Gabriel S. |last7=Chowdhury |first7=Ranasish Roy |last8=Martinez |first8=Quentin |title=3D models related to the publication: The endocranial anatomy of Protocetids and its implications for early whale evolution. |url=https://doi.org/10.18563/journal.m3.264 |website=MorphoMuseuM |language=En |doi=10.18563/journal.m3.264 |date=May 2025}}

References

=Notes=

=Sources=

{{Cite journal

| last = Fraas | first = Eberhard | authorlink = Eberhard Fraas

| title = Neue Zeuglodonten aus dem unteren Mitteleocän vom Mokattam bei Cairo

| url = https://archive.org/stream/neuezeuglodonten00fraa#page/20/mode/2up | access-date = September 29, 2013

}}

{{Cite journal

| last1 = Bianucci | first1 = Giovanni

| last2 = Gingerich | first2 = Philip D. | author2-link = Philip D. Gingerich

| title = Aegyptocetus tarfa, n. gen. et sp. (Mammalia, Cetacea), from the middle Eocene of Egypt: clinorhynchy, olfaction, and hearing in a protocetid whale

| doi = 10.1080/02724634.2011.607985 | bibcode = 2011JVPal..31.1173B

| s2cid = 85995809

}}