Bone Fragment: Whale Or Dolphin Skull?

[Doctor Mud]

I found this bone in spoil piles in New Zealand from the lime mining process.

Unfortunately some things get beat up but I still find some interesting bits and pieces.

To me this looks like cetacean skull material, maybe dolphin?

Haven't a clue what part, but was guessing in the vicinity of the nasal bones or "blow hole"

Could be way off.

Otekaike Limestone ~ 26 million years old

Length on longest axis 10 cm

Four images to follow

"Top"

Edited October 21, 2014 by Doctor Mud

[Doctor Mud]

Underside

[Doctor Mud]

Side view

[Doctor Mud]

"Front"

[Boesse]

Hey Dr. Mud,

That's a bit on the large side for an odontocete; this is almost certainly from a small mysticete. Most likely this is an exoccipital, given the articular surface on one side and smooth surface on the other. Bobby

[Doctor Mud]

Thanks Bobby - I knew you would be able to pin this down.

Hey - I also came across the Geisler article in Nature last night. I haven't had a chance to read it in depth.

(Nature 508: 383 - 386 (April 2014))

From my superficial knowledge I was surprised that this article was Nature material as they only pushed back the evidence for echolocation to 28 mya.

Do the odontocetes that you guys are finding (~ 26 mya) not show evidence for echolocation ability? If they do then Geisler could be on shaky ground given errors that are likely in dating fossils.

I could be wrong.

Sorry if I'm bring up a delicate subject here......

Edited October 22, 2014 by Doctor Mud

[Boesse]

Hey Dr. Mud,

There is one possibly older odontocete from Oregon (Simocetus rayi, described by Ewan in 2002), the updated stratigraphy of which means it could be as old as 28-35 Ma; it has incipient asymmetry and was likely to be an echolocator as well. The age control for Cotylocara is pretty robust.

All the odontocetes from the Oligocene of NZ show various features associated with echolocation, namely cranial asymmetry and a concave facial plane to accommodate the melon.

[Doctor Mud]

Thanks Bobby,

I just wanted to get an impression from someone familiar with the state of play.

Great news for your field that Nature will publish this research.

I see the claims are supported by cladistics and Cotylocera is more "primitive" than the likes of Waipatia that has derived features.

I was just wary of statements surrounding ages as I don't know the precision or accuracy for Oligocene chronology.

I work in the Quaternary, so I use radiocarbon and luminescence dating.

Ages can have uncertainties of greater than 10% e.g 20,000 +\- 2000 years. I know that strontium dating is crucial for tertiary sequences. Seems like the instrumental error can be up to 1 million years. This is just from running replicates.

You would then have to add uncertainty due to assumptions about how the system operates - e.g calibrating strontium ages to absolute ages.

Like I said I'm not a specialist and I just wanted to get a feel of the significance of this paper and how it has been received by the experts ( like yourself)

The cladistics seems pretty robust. My gut reaction about age was, yeah 2 million, could be swallowed up within uncertainty maybe if it was 5 million.