| 词条 | Astraspis |
| 释义 |
| image = Astraspis_desiderata.jpg | image_caption = Astraspis desiderata | fossil_range = {{fossil range|467|443}} middle-late Ordovician | regnum = Animalia | phylum = Chordata | classis = Pteraspidomorphi | subclassis = Astraspida | ordo = Astraspidiformes | genus = †Astraspis | genus_authority = Walcott, 1892 | subdivision_ranks = Species | subdivision =
}} Astraspis ('star shield') is an extinct genus of primitive jawless fish from the Ordovician of Central North America including the Harding Sandstone of Colorado and Bighorn Mountains of Wyoming. It is also known from Bolivia.[1] It is related to other Ordovician fishes, such as the South American Sacabambaspis, and the Australian Arandaspis. DescriptionNearly complete fossils suggest the living animals were about {{convert|200|mm|in|abbr=on}} in length. The body had a mobile tail covered with small protective plate-like scales of less than {{convert|1|mm|in|abbr=on}} and a forebody covered with plate-like scales larger than {{convert|2|mm|in|abbr=on}}. The specimen from North America (described by Sansom et al., 1997) is to have had relatively large, laterally-positioned eyes and a series of eight gill openings on each side. The specimen was generally oval in cross-section. The protective bony plates covering the animal were composed of aspidin (chemically similar to modern shark's teeth), covered by tubercles composed of dentine.[2] It is from these tubercles (which are generally star-shaped) that the name 'Astraspis' (literally "star-shield") is derived. References1. ^Sacabambaspis janvieri. PY Gagnier - Vertébré ordovicien de Bolivie, 1993 2. ^Sansom IJ, Smith MP, Smith MM and Turner P (1997) "Astraspis: The anatomy and histology of an Ordovician fish" Palaeontology, 40 (3): 625–642. Other sourcesMichael J. Benton, Vertebrate Palaeontology, 3rd edition, 2005 External links{{Portal|Paleontology}}
6 : Pteraspidomorphi genera|Ordovician jawless fish|Late Ordovician animals|Ordovician fish of North America|Fossil taxa described in 1892|Prehistoric fish of South America |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。