Pagetia

For the Australian tree, see Bosistoa.

Pagetia Temporal range: Middle Cambrian PreЄ Є O S D C P T J K Pg N

A heavily eroded specimen of Pagetia taijiangensis, 6mm, from Kaili, Guizhou, China
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Trilobita
Order:	Agnostida
Suborder:	Eodiscina
Family:	Eodiscidae
Genus:	Pagetia Walcott, 1916
species
P. bootes Walcott, 1916 (type species) P. bigranulosa Rasetti, 1967 P. billingsi Rasetti, 1945 P. bilobata Lu & Chien, 1978 P. clytia Walcott, 1916 = Mesopagetia clytia P. clytioides Rasetti, 1967 P. connexa (Walcott, 1887) = Microdiscus connexus P. danzhaiensis Zhang, 1980 P. dayongensis Liu, 1982 P. divulgata Bognibova, 1965 P. edura Jell, 1975 P. ellsi Rasetti, 1945 P. erratica Rasetti, 1967 P. fluitata Jell, 1975 P. fossula Resser, 1938 P. gaotaiensis Zhang, 1980 P. hainesi Laurie, 2006 P. horrida Lermontova, 1951 P. howardi Jell, 1975 P. inermis (Rasetti, 1966) = P. billingsi inermis P. inferstrix Jell, 1975 P. jingheensis P. laevis Rasetti, 1967 P. latilimbata Chien, 1961 P. leptoskolos Jell, 1975 P. longispina Palmer & Gatehouse, 1972 P. luoyacunensis Lin & Jago 1993 P. macrommatia Jell, 1975 P. maladensis Resser, 1939 P. miaoubanpoensis P. morrisi Laurie, 2006 P. ocellata Jell, 1970 P. oepiki Jell, 1975 P. parabootes Zhang, 1981 P. pollusta Jell, 1975 P. polygnota Jell, 1975 P. prolata Jell, 1975 P. quebecensis Rasetti, 1966 P. rasettii Young & Ludvigsen, 1989 P. resseri Kobayashi, 1943 P. rugosa Rasetti, 1966 P. salebra Jell, 1975 P. salva Lu & Qian P. significans Ethelridge, 1902 = Eopagetia significans P. silicunda Jell, 1975 P. sinesculata P. skraelingi Young & Ludvigsen, 1989 P. spiniger P. stenoloma Palmer, 1968 P. taijiangensis Yuan & Zhao, 1997 P. thornstonensis Jell, 1975 P. triaena Jell, 1975 P. venusta P. walcotti Rasetti, 1966 P. whithousei Jell, 1975^[1]
Synonyms
Eopagetia, Mesopagetia

Pagetia is a genus of very small trilobites, assigned to the Agnostida order, Eodiscidae family, that had a global distribution and lived during the Middle Cambrian. It contains 55 currently recognized species, each with a limited spatial and temporal distribution.

Taxonomy

Species previously assigned to Pagetia

P. attleborensis = Hebediscus attleborensis
P. jinnanensis = Sinopagetia jinnanensis
P. maladensis = Macannaia maladensis
P. medicinalis (plant, Rutaceae) = Bosistoa medicinalis
P. monostylis (plant, Rutaceae) = Bosistoa medicinalis

Description

The head shield (or cephalon) and tail shield (or pygidium) are approximately of the same size and shape like in other Agnostida, with eyes, free cheeks and proparian sutures. There is no well-defined furrow between the front of the glabella and the anterior border furrow. The glabella is well defined, slightly tapering forward, with a large subhorizontal spine extending from the back of the glabella. The anterior border furrow usually shows a series of radiating ridges (like spokes), a widespread feature among eodiscids. There are no spines extending from the angle between the side and the back of the cephalon (called genal spines). The 2 thoracic segments each consisting of a horizontal inner portion that abruptly passes into an inclined outer portion (fulcrate). The lateral tip of the frontal segment points backwards, while that of the rear segment points forwards, to enable enrolment. The axis in the pygidium (or rhachis) is well defined, reaches or overhangs the posterior border and usually has five distinctive rings and is extended backwards in a firm spike.^[2] Because eyes, spines and spikes are fragile features, these may be lost through erosion in many specimens.

The palate (or hypostome) is a convex (the centre bulging down), subquadrate plate, positioned directly under the frontal part of the glabella. It is comparable to hypostomes of other trilobites and provides an argument that Agnostida can be regarded as specialized, simplified trilobites. ^[3]

Ecology

Several species of Pagetia are known from the Burgess Shale. 1022 specimens of Pagetia are known from the Greater Phyllopod bed, where they comprise 1.94% of the community.^[4] Its remains are sometimes found in the otherwise-empty tubes of the polychaete worm Selkirkia.^[5]^[6]

External links

"Pagetia bootes". Burgess Shale Fossil Gallery. Virtual Museum of Canada. 2011.

References

↑ Lin, J.-P.; Yuan, J.-L. (2009). "Reassessment of the mode of life of Pagetia Walcott, 1916 (Trilobita: Eodiscidae) based on a cluster of intact exuviae from the Kaili Formation (Cambrian) of Guizhou, China". Letaia 42: 67–73. doi:10.1111/j.1502-3931.2008.00104.x.
↑ Rasetti, F. (1966). "Revision of the North American species of the Cambrian trilobite genus Pagetia". Journal of Paleontology 40 (3): 502–511.
↑ Öpik, A.A. (1952). "The hypostoma of Pagetia". Journal of Paleontology 26 (2): 272–274.
↑ Caron, Jean-Bernard; Jackson, Donald A. (October 2006). "Taphonomy of the Greater Phyllopod Bed community, Burgess Shale". PALAIOS 21 (5): 451–65. doi:10.2110/palo.2003.P05-070R. JSTOR 20173022.
↑ Chatterton, B. D. E.; Collins, D. H.; Ludvigsen, R. (2003). "Cryptic behaviour in trilobites: Cambrian and Silurian examples from Canada, and other related occurrences". In Lane, P. D; Siveter, D. J; Fortey, R. A. Trilobites and Their Relatives. Special Papers in Palaeontology 70. The Palaeontological Association. pp. 157–173. ISBN 9780901702814.
↑ Coppold, Murray and Wayne Powell (2006). A Geoscience Guide to the Burgess Shale, p.56. The Burgess Shale Geoscience Foundation, Field, British Columbia. ISBN 0-9780132-0-4.

This article is issued from Wikipedia - version of the Friday, May 01, 2015. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.