The Emergence of Whales, Chp. 7

Synopsis of Chapter 7, “Middle Eocene Cetaceans from the Harudi and Subathu Formations of India”

by Sunil Bajpai, Dept. of Earth Sciences, Univ. of Roorkee, Uttar Pradesh, India

J.G.M Thewissen, Dept. of Anatomy, Northeastern Ohio Universities College of Medicine, Rootstown, OH

Eocene cetaceans first reported from India in 1971, from Kachchh (formerly Kutch/Cutch) (a southeastern coastal province bordering Pakistan and the Arabian Sea)

Remingtoncetus and Andrewsiphius in 1986

Two locations yielded fossils in this study:
– western base of Babia Hill
– modern rivercut about 2 km north of Harudi to several km west mostly dry during the dry season

Geological units for both locales are diagrammed: Limestone, shales, gypsum, with overlying foraminiferal or nummulitic/coral limestone in the Oligocene They write that fossils and gypsum occur at several levels on Babia Hill, so the units may not be “stratigrapically meaningful”. The Harudi formation was described in Chapter 1, and I’ll copy it in here:

“Domanda and Harudi are interbedded red-brown and green shales, silty marls, thin oyster-rich limestones. Interpreted as offshore shallow marine to distal carbonate-rich environments. –> differentiation of environment between remingtoncetids and protocetids ??? More certain, remingtoncetids and protocetids occupied coastal marine waters with some freshwater influence.”

Remingtoncetus Remingtoncetus harudiensis, Sahni and Mishra 1975
Cranial fragments with teeth. Some pictures are provided.

Remingtoncetus sloani, Sahni and Mishra 1975
Upper skull lacking braincase, lower skull with teeth, this study found more pieces

Andrewsiphius kutchensis, Sahni and Mishra 1975 Partially complete cranium, plenty of teeth

“The new skull of Andrewsiphius shows that this genus is very different from Remingtoncetus and that the Remingtoncetidae as a group are strongly specialized.” After describing the differences, they also describe features that are “surprisingly different” from the other protocetids.

Protocetids Indocetus ramani, Sahni and Mishra, 1975 Cranial fragments The new specimens described here “cover some anatomical areas previously unknown in Indocetus” (it pays to go back and find more pieces)

Indocetus is only known from Kachchh. Other “candidate” Indoceti have been withdrawn. Rodhocetus is very similar and all of the differences are essentially postcranial (I did not know that!)

Babiacetus mishrai (New species) Based on jaw fragment with teeth pages 226-228 have discussion and diagrams of the teeth

This specimen is “easily identified as a protocetid on the basis of the large mandibular foramen and lingually concave ascending ramus”

Jaw structure indicates the temporal muscle had become a weak jaw closer, but all other indications indicate that powerful jaw closing was an important part of the feeding behavior of Babiacetus

Basilosaurids

Gaviacetus, Gingerich et al. 1995
Skull has exceptionally narrow rostrum caudal vertebrae of basilosaurid found with it, no other similarly sized cetaceans from Kachchh.

Gaviacetus sahnii (New species)
fragmentary skull, similar to Gaviacetus razai, but with smaller teeth, and some caudal vertebrae

This is the largest cetacean known from Kachchh.

** Description of another tooth in the Subathu formation, a different location. First cetacean part found in clearly marine sediments (near a marine turtle fossil). Expectation is that further work will yield more fossils.

Summary/Conclusions (told you this was short)

– The Harudi formation shows a remarkable diversity of early cetaceans

– The cetacean faunas of the Domanda and Drazinda formations are similar to the Harudi formation

– Indocetus and Rodhocetus are essentially similar; Rodhocetus is differentiated due to the presence of a large amount of post-cranial skeleton

– Further collecting effort in India will likely yield much more cetacean fossil material

That’s it. Prepare to be blown away by Chapter 8:

“Postcranial osteology of the North American Middle Eocene Protocetid Georgiacetus”