“Dolichorhynchops herschelensis”的意思、由来-开放百科全书

Dolichorhynchops herschelensis (meaning ‘long-nosed face’ from Herschel) is an extinct species of polycotylid plesiosaur, and one of two species in the genus Dolichorhynchops, dating from the Late Cretaceous. There are only three known specimens of the animal and all were recovered from a bone bed at Ancient Echoes Interpretive Centre near the town of Herschel, Saskatchewan, from which the specie's name is derived, in the 1990s. Like dinosaurs, it is believed that Dolichorhynchops Herschelensis went extinct about 65 million years ago.

Description

Dolichorhynchops herschelensis was an ocean-going, short-necked, marine reptile. It looked similar to other members of the Dolichorhynchops genus but was somewhat smaller, measuring about 3 m in length. Like others in the genus, it had four large flippers with both the fore and hind limbs being of a similar size. In addition, it had a short body and tail as well as relatively large head at the end of a short, stout neck, with a long snout sporting a mouth full of fine, conical teeth.^[1]

Historical range

Dolichorhynchops herschelensis is only known from the one specimen collected near Herschel, Saskatchewan.^[1] However, other members of Dolichorhynchops have been found throughout North America on land formerly submerged by the Western Interior Seaway, including Saskatchewan. In fact several Dolichorhynchops fossils have been discovered in the same bone bed as Dolichorhynchops Herschelensis.

Age

Dolichorhynchops herschelensis lived in the Late Cretaceous period (about 70 million years ago), when the last remnants of the Western Interior Seaway still covered much of Saskatchewan. The deposits that contain the Herschel plesiosaur, belong to a rock formation called the Bearpaw Formation, which is found in much of southern Saskatchewan.

Habitat

Fossils contained in the Bearpaw Formation suggest that the Western Interior Seaway, which Herschelensis inhabited, was shallow and muddy around 70 million years ago with a warm, tropical climate similar to that of present day Florida. The waters that Herschelensis were swimming in, were teeming with other large predators, including several species of mosasaurs, ichthyosaurs and long-necked plesiosaurs. Giant prehistoric turtles, as well as several species of bony fish, including Pachyrhizodus, Enchodus, and the huge Xiphactinus, In addition to sharks, such as Squalicora, swam in the warm waters while giant clams called Inoceramus , and shelled invertebrates like ammonites and baculites inhabited the seaway's muddy bottom .^[2]

Diet

The Dolichorhynchops herschelensis was a predatory carnivore. Its long snout, and fine, cone-like teeth suggest that they were designed to pierce small soft-bodied prey - most likely fish. The shape of body of Dolichorhynchops herschelensis supports this in that it appears to have been a highly manoeuvrable pursuit predator, suited to chasing fish.^[3] Fossils of several potential prey animals that swam in the waters of the Western Interior Seaway alongside Dolichorhynchops Herschelensis, have been found in the same fossil bone bed.

Related species

Dolichorhynchops belongs to a group called short-necked plesiosaurs or polycotylids. Dolichorhynchops Osborni, Dolichorhynchops Bonneri and Dolichorhynchops Tropicensis are also members of the Dolichorhynchops genus. Elasmosaurs (long-necked plesiosaurs) are also closely related.

Classification

Discovery

In 1990 the first fossilized remains of a young, adult plesiousaur, later named Dolichorhynchops Herschelensis, were discovered in the Coalmine Ravine near Herschel, Saskatchewan. The skeleton was discovered in a disarticulated state with the bones scattered around the dig site. The skull, lower jaw, ribs, pelvis and shoulder blades were all recovered, but the spine was incomplete, so the exact number of vertebrae the living animal would have had is unknown. All four limbs are missing, with the exception of 9 small phalanges (finger bones) and a small number of limb bones found close by which may belong to the animal in question.

The skeleton was subsequently excavated and moved to the Royal Tyrrel Museum in Drumheller, Alberta for analysis and preservation. The bone bed where the plesiousaur was discovered was discovered by Tim Tokaryk of the Royal Saskatchewan Museum in the 1990s.^[4] The marine bone bed contains a variety of fossils of short and long-necked plesiosaurs (polycotylids & elasmosaurs), mosasaurs, several species of shark, and many types of bony fish. In 1997, two additional fossilized plesiosaur skeletons were discovered at the site and in 2005, the remains were deemed a completely new species by Dr. Tamaki Sato, a Japanese vertebrate paleontologist. Excavations continue at the site.^[5]

Preservation

The Western Interior Seaway was probably less than 600 feet deep in most areas, and had a relatively flat and soft, oxygen-depleted mud bottom that was ideal for fossilization. After dying, Herschelensis would have sunk to the muddy sea floor where it was quickly covered and the fossilization process began.

The skeleton remained buried in the ground for millions of years. After being excavated from the ground around Herschel, the original Dolichorhynchops herschelensis fossil was taken to the Royal Tyrrell Museum of Palaeontology in Drumheller, Alberta. Subsequent fossil finds were sent to the T. rex Discovery Centre in Eastend, Saskatchewan for preparation and cataloguing.^[5]

Ancient Echoes Interpretive Centre

Ancient Echoes Interpretive Centre, located in Herschel, Saskatchewan, close to the site where the fossils were discovered, is the home of Dolichorhynchops herschelensis. The Centre has been designated as a Municipal heritage site by the province of Saskatchewan. In addition to being home to important First Nations archaeology sites, the Centre houses several exhibits related to the area’s ancient history, including many marine and terrestrial fossils. Tours of the fossil dig sites are available. ^[6]

References

1. ^{{Cite web|url=https://www.researchgate.net/publication/250070792_A_new_polycotylid_plesiosaur_Reptilia_Sauropterygia_from_the_Upper_Cretaceous_Bearpaw_Formation_in_Saskatchewan_Canada|title=A new polycotylid plesiosaur (Reptilia : Sauropterygia) from the Upper Cretaceous Bearpaw Formation in Saskatchewan, Canada|website=ResearchGate|language=en|access-date=2019-01-27}}
2. ^¹{{Cite web|url=http://royalsaskmuseum.ca/pub/Fossil%20Video%20Contest/short-neck_english.pdf|title=Herschel Short-necked Plesiosaur|last=|first=|date=|website=royalsaskmuseum.ca/|archive-url=|archive-date=|dead-url=|access-date=}}
3. ^{{Cite web|url=http://plesiosauria.com/diet/|title=Diet|website=Plesiosaur Directory|language=en-US|access-date=2019-01-29}}
4. ^{{Cite web|url=https://royalsaskmuseum.ca/rsm/education/blog/exploring-in-herschel-saskatchewan|title=Exploring in Herschel, Saskatchewan « Royal Saskatchewan Museum|website=royalsaskmuseum.ca|access-date=2019-01-27}}
5. ^¹{{Cite web|url=https://royalsaskmuseum.ca/trex/education/blog/paradise-found|title=Paradise Found! Exploring Saskatchewan’s Lost Beach Front Property « T.rex Discovery Centre|website=royalsaskmuseum.ca|access-date=2019-01-27}}
6. ^{{Cite web|url=https://www.ancientechoes.ca/|title=Ancient Echoes Interpretive Centre|last=|first=|date=|website=www.ancientechoes.ca|archive-url=|archive-date=|dead-url=|access-date=2019-01-27}}