Crossopholis
| Crossopholis | ||||||||||||
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Crossopholis magnicaudatus |
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| Temporal occurrence | ||||||||||||
| Ypresium (lower Eocene) | ||||||||||||
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Crossopholis | ||||||||||||
| Cope , 1883 |
Crossopholis is an extinct genus and species ( Crossopholis magnicaudatus ) from the sturgeon orderthat lived in the Ypresium about 52 million years ago. The fossils were discovered in the area of the Fossil Butte National Monument .
discovery
The species was described by Edward Drinker Cope in 1883 using an incomplete body and tail fossil . In 1886 Cope was able to recover a partially preserved skull. An almost complete fossil could only be recovered in 1980 because the species is rare and there are great similarities to other species from the same fossil deposit.
features
Crossopholis were medium-sized fish (1.5 m) with a plump, stocky body than today's sturgeon species. The body was covered with thousands of tiny scales (≤ 0.5 mm), as the scientific name suggests. The fins were relatively large and the caudal fin heterocerk . The lower caudal fin lobe was relatively large and wider than the upper one. The head was broad, the rostrum elongated and pointed. The mouth was submissive . The dorsal, ventral and anal fins were located in the rear half of the body, the anal fin still at an angle behind the dorsal fin. Research suggests that the rostrum served as an electrical organ , similar to that of the living relatives of the species.
Location
Fossils of the species were discovered in the area of Fossil Lake from the area of the Green River Formation . It is more common in the shallow deposits of the Thompson Ranch Sandwich Bed in the northeast corner of the deposit than in the deeper sedimentary deposits of the middle of the lake. The rarity of the species has been explained by the fact that Crossopholis may have lived in the rivers in the north of the area. This thesis is confirmed by the fact that no juvenile fish were found in the sea area.
food
Crossopholis was a predatory fish. Fossils have been found whose stomach contents consisted of the remains of small schooling fish ( Knightia eocaena ). The relatives living today ( paddlefish ), on the other hand, feed mainly on zooplankton .
Systematics
As a member of the family Polyodontidae is Crossopholis closely allied to still living paddlefish . Crossopholis means "rough scales"; a reference to the thousands of tiny scales and magnicaudatus is Latin for "large fins".
Individual evidence
- ^ British Museum (Natural History). Dept. of Geology, Arthur Smith Woodward: Catalog of the Fossil Fishes in the British Museum (Natural History): Actinopterygian Teleostomi of the orders Chondrostei (concluded), Protospondyli, Aetheospondyli, and Isopondyli (in part). 1895.
- ↑ † Crossopholis Cope 1883. Paleobiology Database, Fossilworks 2017.
- ↑ a b c Lance Grande: The Lost World of Fossil Lake: Snapshots from Deep Time . University of Chicago Press, 2013, ISBN 978-0-226-92296-6 ( google.com ).
- ↑ Melvin L. Warren, Jr., Brooks M. Burr: Freshwater Fishes of North America: Volume 1: Petromyzontidae to Catostomidae . JHU Press, 2014, ISBN 978-1-4214-1201-6 ( google.com ).
literature
- Lance Grande: The Lost World of Fossil Lake: Snapshots from Deep Time. University of Chicago Press, 2013, ISBN 978-0-226-92298-0 , pp. 112, 141, 178-180, 352. (books.google.de)
- Vadim J. Birstein, John R. Waldman, William E. Bemis: Sturgeon biodiversity and conservation. In: Developments in Environmental Biology of Fishes. Volume 17, Springer Science & Business Media, 2006, ISBN 0-306-46854-9 . (books.google.de)