Hemicyclaspis murchisoni - Object of the Month

Plamen, PhD student.School of Geography, Earth and Environmental Sciences, talks about his choice of the Object of the Month.

Title: Object of the Month - Hemicyclaspis murchisoni - Lapworth Museum of Geology

Duration: 2.12 mins

Speaker Names (if given): S1 Plamen, PhD student

S1  My name is Plamen, I'm a third year PhD student in the University of Birmnigham. My project deals with fossil sharks but today I'm going to present something different and it's a really bizarre looking jawless fish from the Upper Silurian.

There is a big morphological gap between jawless vertebrates and jawed vertebrates and this gap is filled in mainly by fossil taxa from the Paleozoic. It's a really diverse group of jawless fish from the Paleozoic. Studying these groups is really important to understand a major transition in the evolutionary history of vertebrates which is the origin of jawed vertebrates, or jawed fish. One of the most interesting groups in that respect is the osteostracans which are considered as a group which is the most closely related to jawed fish because they exhibit some really derived characters. We have a lot of osteostracan specimens here in the museum but this one here is particularly important because it shows pretty much the whole fish, minus the tail. So we have the head and the body attached to each other.

This specimen was donated to the museum in 1974. It comes from the Coronal Sandstone which had been dated at that time as Carboniferous but after the discovery of this specimen we know now that the age of this rock formation is Upper Silurian. If we look at a model of a closely related genus you can see some of the derived features of osteostracans and particularly these pectoral fins. Osteostracans possess a really important feature that, kind of, links them to jawed vertebrates and that's the development of paired fins and it's through examination of such well preserved specimens that we know about that because, in this specimen, you can them right here.

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