Tympanic bulla -- from what?

[jbstedman]

This piece of a tympanic bulla is 1 1/2" long. I found it in the Calvert Formation, which is mid-Miocene.

I don't know if there is enough here (not an intentional pun ) to identify what animal this came from. From my literature search I assume my choices are whale or dolphin. True? Genus and species? Thanks for your help.

[Metopocetus]

This piece of a tympanic bulla is 1 1/2" long. I found it in the Calvert Formation, which is mid-Miocene.

I don't know if there is enough here (not an intentional pun ) to identify what animal this came from. From my literature search I assume my choices are whale or dolphin. True? Genus and species? Thanks for your help.

Almost certainly whale...boesse might be able to tell you Genus and species from what you have.

[Carl O'Cles]

Almost certainly whale...boesse might be able to tell you Genus and species from what you have.

For knowledge purposes what about this makes you think whale? My guess would have been some type of dolphin based soley on the size. I know this a very bad practice because not all whales are huge and also whales have babies and all which would have smaller earbones but typically the bulla's i attribute to whale are close to fist size.

[Boesse]

Howdy all,

Technically "whale" is correct, but it is not from a baleen whale. Its from a toothed whale. What kind specifically... good question.

I suspect that this bulla is from a "River" Dolphin, or a member of the Platanistidae.

However, I'll check with some publications tommorrow - the Calvert Fm. odontocete assemblage is highly diverse, and includes "Kentriodontid" dolphins, longirostrine Eurhinodelphids, extinct "river dolphin" platanistids such as Araeodelphis and Zarchachis, and medium to gigantic shark-toothed squalodontid whales. Oh, and Ziphiids (beaked whales) and some sperm whales (like the fearsome Orycterocetus crocodylinus).

Tympanics aren't terribly diagnostic, and in some cases *can* be for the family level... but typically never for the genus level.

And lastly, baleen whales have tympanics that do not change in size during growth. In other words, a humpback whale calf will have a tympanic fully formed at birth the same size as the mother. Its kinda freaky - I think it is similar in odontocetes.

Bobby

[jbstedman]

Technically "whale" is correct, but it is not from a baleen whale. Its from a toothed whale. What kind specifically... good question.

I suspect that this bulla is from a "River" Dolphin, or a member of the Platanistidae.

However, I'll check with some publications tommorrow - the Calvert Fm. odontocete assemblage is highly diverse, and includes "Kentriodontid" dolphins, longirostrine Eurhinodelphids, extinct "river dolphin" platanistids such as Araeodelphis and Zarchachis, and medium to gigantic shark-toothed squalodontid whales. Oh, and Ziphiids (beaked whales) and some sperm whales (like the fearsome Orycterocetus crocodylinus).

Tympanics aren't terribly diagnostic, and in some cases *can* be for the family level... but typically never for the genus level.

And lastly, baleen whales have tympanics that do not change in size during growth. In other words, a humpback whale calf will have a tympanic fully formed at birth the same size as the mother. Its kinda freaky - I think it is similar in odontocetes.

Bobby

Thanks for this posting. What are the attributes of this bulla that indicated it was from a toothed whale and not a baleen whale? Its size?

Whoa, I wasn't aware of the staggering diversity of the toothed whale assemblage in the Calvert. (I guess this helps explain the presence of megatoothed shark teeth in this formation.)

[Boesse]

Thanks for this posting. What are the attributes of this bulla that indicated it was from a toothed whale and not a baleen whale? Its size?

Whoa, I wasn't aware of the staggering diversity of the toothed whale assemblage in the Calvert. (I guess this helps explain the presence of megatoothed shark teeth in this formation.)

Size and shape - odontocetes are smaller, and have smaller bullae, and vice versa for mysticetes. Also, odontocetes have 'pointed' tympanics to a degree, and there are some other differences, such as a biloped bulla, etc.

Bobby

[Carl O'Cles]

And lastly, baleen whales have tympanics that do not change in size during growth. In other words, a humpback whale calf will have a tympanic fully formed at birth the same size as the mother. Its kinda freaky - I think it is similar in odontocetes.

Bobby

Thats quite interesting....You learn something new every day, thanks for the info

[Boesse]

Ya, well, what good is knowledge if you don't disseminate it to other people, right? Sharing knowledge is my major goal in life.