Ian who is 10, asked us.....
Do you know if there are any shark fossils that are more than 365 million years old?
Fossil fragments of fish on the lineage leading to sharks date back 455 million years ago. In 2003, scientists reported discovering an articulated skeleton of a shark relative called Doliodus problematicus that lived almost 409 million years ago. Here's the abstract of the paper.
Ian also expressed an interest in moving animals, so here is a link to a page about locomotion (how animal move) at Leeds University in England. There are some nice videos here of some very early work done (in the 1870's!) on locomotion by the English scientist Edueard Muybridge. He used a special system of cameras to make a series of photographs of animals to see how they moved and then reassebled them into an early form of film.
posted by Q & A @ 3:30 AM
3 comments
3 Comments:
Thanks! The abstract of the shark article was great.
I have another question. Do you know if there have been any new fossil discoveries of desmostylans and/or sea cows in the past few years? I was wondering if desmostylans are more closely related to sea cows, elephants or hyraxes.
Thank you,
Ian the Question Man, age 10
The latest studies of desmostylians indicate that they are more closely related to elephants than they are to hyraxes or sea cows. Within the placental mammal group Paenungulata (it includes hyraxes, sea cows and elephants), the desmostylians and elephants form a subgroup termed the Behemota, with the features that indicate their relatedness mostly being details of the teeth and ear region.
Another group - the obscure and poorly known anthracobunids - also appear to be members of Behemota (interestingly, anthracobunids are like desmostylians in being aquatic or amphibious. Given that elephants are also within this group, you might like to think what this tells us about the ancestry of elephants).
New fossil desmostylians and sea cows are published fairly regularly. One of the biggest discoveries within this area has been the 2001 publication of the Jamaican fossil sea cow Pezosiren - it is significant in that it still had hindlegs and could walk on land.
the earliest jawed fish i belive is to a fish with the genus of archeaonodontalepis. whicth i found a tooth of,in Marion city,Ohio that i belive that is between 445 to 460 million years old, in the ordovician period.so this shark like fish could be the ancestors of doliodus and maybe acanthodian and could also be the desendents of a earlier form ofa thelodont. It might of been a family or genus at the time that evolved rapidley.AlL by the way my name is Lucas w.pierce of St. main steet in Marion.OHIO....
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