Pentacrinites

Last updated

Pentacrinites
Temporal range: Hettangian-Bathonian
Pentacrinites NT.jpg
A drawing of Pentacrinites
Scientific classification Red Pencil Icon.png
Kingdom: Animalia
Phylum: Echinodermata
Class: Crinoidea
Order: Isocrinida
Family:† Pentacrinitidae
Genus:† Pentacrinites
Blumenbach, 1804
Species
  • P. fossilisBlumenbach, 1804 (type) = P. britannicus
  • P. dargniesi(Hess, 1972) = Extracrinus dargniesi
  • P. dichotomus(McCoy, 1848)
  • P. doreckaeSimms, 1989
  • P. quenstedtiOppel, 1856 = Pentacrinus quenstedti

Pentacrinites is an extinct genus of crinoids that lived from the Hettangian to the Bathonian of Asia, Europe, North America, and New Zealand. Their stems are pentagonal to star-shaped in cross-section and are the most commonly preserved parts. [1] Pentacrinites are commonly found in the Pentacrinites Bed of the Early Jurassic (Lower Lias) of Lyme Regis, Dorset, England. [2] Pentacrinites can be recognized by the extensions (or cirri) all around the stem, which are long, unbranching, and of increasing length further down, the very small cup and 5 long freely branching arms. [3]

Contents

Description

Like most echinoderms, Pentacrinites was composed of numerous calcite plates which were arranged into different body parts. Pentacrinites had 3 kinds of body parts: arms, cup (calyx or theca) and stem. The stem consisted of a stack of numerous 5-sided beads (or columnal plates) with a canal at their centre. The stem had flexible appendages (or cirri) that were used to attach an individual. These cirri themselves were connected to specialized columnals called nodals, leaving oval scars after breaking off. The cirri consisted of diamond-shaped plates with a central canal, less flatted further from the stem. [4] The cup-shaped calyx was very small and consisted of two bands of five plates. These were the bases of the five arms. The top of the calyx was covered by numerous small polygonal plates and the mouth and anus were found on this surface.

The arms divide frequently, like tree branches, so that at the top end there could be over 50 branches in all. The arms were formed of piles of calcite plates. The arms carried many thin feeding branches (or pinnae, like a fern frond). These pinnae had tube feet, that were covered in mucus, reached into the water and caught plankton. These arms were not very mobile. The arms plates of the arms have an insertion, that formed a grove that ran along the length of the arm and onto the calyx. This served to transport the food particles to the mouth. [3]

Taxonomy

Pentacrinites dichotomus Pentacrinites dichotomus.JPG
Pentacrinites dichotomus

Pentacrinites may have evolved from early, free living isocrinids, which occur today on the sea floor. [3]

Reassigned species

Ecology

Pentacrinites is a floating sea lily that was attached to driftwood during its adult life. This pseudo-planktonic lifestyle enabled it to exploit food unavailable to other crinoids. [5]

Distribution

Pentacrinites became extinct and has left no direct living descendants. Its remains have been found in many different locations, suggesting it occurred throughout the world's oceans. Free living isocrinids however, still populate the seas, usually at over 150m deep. [3]

Related Research Articles

The Jurassic is a geologic period and stratigraphic system that spanned from the end of the Triassic Period 201.3 million years ago (Mya) to the beginning of the Cretaceous Period, approximately 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era and is named after the Jura Mountains, where limestone strata from the period were first identified.

Crinoid Class of echinoderms

Crinoids are marine animals that make up the class Crinoidea, one of the classes of the phylum Echinodermata, which also includes the starfish, brittle stars, sea urchins and sea cucumbers. Those crinoids which, in their adult form, are attached to the sea bottom by a stalk are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, being members of the largest crinoid order, Comatulida.

<i>Plesiosaurus</i> Extinct genus of reptiles

Plesiosaurus is a genus of extinct, large marine sauropterygian reptile that lived during the early part of the Jurassic Period, and is known by nearly complete skeletons from the Lias of England. It is distinguishable by its small head, long and slender neck, broad turtle-like body, a short tail, and two pairs of large, elongated paddles. It lends its name to the order Plesiosauria, of which it is an early, but fairly typical member. It contains only one species, the type, Plesiosaurus dolichodeirus. Other species once assigned to this genus, including P. brachypterygius, P. guilielmiimperatoris, and P. tournemirensis have been reassigned to new genera, such as Hydrorion, Seeleyosaurus and Occitanosaurus.

<i>Scelidosaurus</i> Genus of reptiles (fossil)

Scelidosaurus is a genus of herbivorous armoured ornithischian dinosaur from the Jurassic of the British Isles.

<i>Sarcosaurus</i> Extinct genus of dinosaurs

Sarcosaurus is a genus of basal neotheropod dinosaur, roughly 3.5 metres (11 ft) long. It lived during the Hettangian-Sinemurian stages of the Early Jurassic, about 199-194 million years ago. Sarcosaurus is one of the earliest known Jurassic theropods, and one of only a handful of theropod genera from this time period. Along with Dracoraptor hanigani it is one of the two described neotheropods from the lowermost Jurassic of the United Kingdom.

Saltrio Formation

The Saltrio Formation is a geological formation in Italy. It dates back to the middle Sinemurian, and would have represented a pelagic or near-epicontinental environment, judging by the presence of marine fauna such as the nautiloid Cenoceras. The Fossils of the Formation were described on the late 1880s and revised on 1960s, finding first marine biota, such as Crinoids, Bivalves and other fauna related to Epicontinental basin deposits.

Blue Lias Triassic/Jurassic geological formation in the UK

The Blue Lias is a geological formation in southern, eastern and western England and parts of South Wales, part of the Lias Group. The Blue Lias consists of a sequence of limestone and shale layers, laid down in latest Triassic and early Jurassic times, between 195 and 200 million years ago. The Blue Lias is famous for its fossils, especially ammonites.

Fossils of many types of water-dwelling animals from the Devonian period are found in deposits in the U.S. state of Michigan. Among the more commonly occurring specimens are bryozoans, corals, crinoids, and brachiopods. Also found, but not so commonly, are armored fish called placoderms, snails, sharks, stromatolites, trilobites and blastoids.

Encrinus is an extinct genus of crinoids, and "one of the most famous". It lived during the Late Silurian-Late Triassic, and its fossils have been found in Europe.

Comatulida is an order of crinoids. Members of this order are known as feather stars and mostly do not have a stalk as adults. The oral surface with the mouth is facing upwards and is surrounded by five, often divided rays with feathery pinnules. Comatulids live on the seabed and on reefs in tropical and temperate waters.

Anningasaura is an extinct genus of basal plesiosaur. It is known from a single type species, A. lymense, discovered in Early Jurassic rocks of Lyme Regis in the United Kingdom.

<i>Metacrinus rotundus</i> Species of crinoid

Metacrinus rotundus, the Japanese sea lily, is a marine invertebrate, a species of stalked crinoid in the family Isselicrinidae. It is a species found off the west coast of Japan, and is living near the edge of the continental shelf, around 100–150m deep. This is the shallowest species among the extant stalked crinoids.

<i>Agaricocrinus americanus</i> Species of echinoderm

Agaricocrinus americanus, the mushroom crinoid, is a species of extinct crinoid, known only from its fossils, which are found in the U.S. states of Indiana, Tennessee and Kentucky. They date back to the Lower Mississippian, about 345 million years ago.

<i>Antedon mediterranea</i> Species of crinoid

Antedon mediterranea is a species of stalkless crinoid in the family Antedonidae, commonly known as the Mediterranean feather star. It is found on the seabed at moderate depths in the Mediterranean Sea. It is a filter feeder and captures plankton with its long feathery arms.

Bourgueticrinida is an order of crinoids that typically live deep in the ocean. Members of this order are attached to the seabed by a slender stalk and are known as sea lilies. While other groups of crinoids flourished during the Permian, bourgueticrinids along with other extant orders did not appear until the Triassic, following a mass extinction event in which nearly all crinoids died out.

Cenocrinus is a monotypic genus of stalked crinoids in the family Isselicrinidae. The great West Indian sea lily is the only species in the genus and is found in deep waters in the Caribbean Sea and Gulf of Mexico.

Agaricocrinus is a genus of extinct crinoids, belonging to the family Coelocrinidae.

<i>Dracoraptor</i> Genus of reptiles (fossil)

Dracoraptor is a genus of coelophysoid dinosaur that lived during the Hettangian stage of the Early Jurassic Period of what is now Wales, sometime between 201 to 199 million years ago. It was discovered in 2014 at the Blue Lias Formation of the United Kingdom, and named in 2016 by British palaeontologist David Martill and colleagues, with the type species being Dracoraptor hanigani.

Delocrinus is a genus of extinct crinoids, belonging to the family Catacrinidae. Specimens have been found in Kansas Missouri Nebraska Nevada Oklahoma, Arizona, Iowa, Texas, Utah and Virginia.

<i>Notocrinus virilis</i> Species of crinoid

Notocrinus virilis is a marine invertebrate, a species of crinoid or feather star in the family Notocrinidae. It is found in deep water in the Southern Ocean around the coasts of Antarctica and adjacent islands. A sea snail sometimes parasitizes it.

References

  1. ↑ Hamilton, R. 1975. Fossils and Fossil Collecting. London: Hamlyn Publishing.
  2. ↑ Davies, G. M. 1964. The Dorset Coast: A Geological Guide. London: A & C Black.
  3. 1 2 3 4 Natural History Museum. "Pentacrinites fossilis - Taxonomy". NHM Website.
  4. 1 2 Hunter, A.W.; Oji, T.; Okazaki, Y. (2011). "The occurrence of the pseudoplanktonic crinoids Pentacrinites and Seirocrinus from the Early Jurassic Toyora Group, western Japan". Paleontological Research. 15 (1): 12–22. doi:10.2517/1342-8144-15.1.012. S2CID   130057366.
  5. ↑ Simms, M.J. (1999). "22 –Pentacrinites from the Lower Jurassic of the Dorset Coast, Southern England". In Hess, H.; Brett, C.E.; Ausich, W.I.; et al. (eds.). Fossil Crinoids. Cambridge: Cambridge University Press. ISBN   9780521524407 . Retrieved 2014-01-27.

Sources

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.