Cyathaspidiformes

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Cyathaspidiformes
Temporal range: Silurian-Devonian
Cyathaspis banksii.jpg
Reconstruction of Cyathaspis banksii
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Pteraspidomorphi
Subclass: Heterostraci
Order:Cyathaspidiformes
Suborders, Superfamilies and Families

Cyathaspidiformes is an extinct order of heterostracan vertebrates known from extensive fossil remains primarily from Silurian to Early Devonian strata of Europe, and North America, and from Early Devonian marine strata of Siberia.

In biological classification, the order is

  1. a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family. An immediately higher rank, superorder, may be added directly above order, while suborder would be a lower rank.
  2. a taxonomic unit, a taxon, in that rank. In that case the plural is orders.
Heterostraci subclass of fishes (fossil)

Heterostraci is an extinct subclass of pteraspidomorph jawless vertebrate that lived primarily in marine and estuary environments. The first identifiable heterostracans appear in the fossil record during the early Silurian, and all, save for the Psammosteids, became extinct by the start of the late Devonian. This last group of heterostracans died out in the extinction event at the end of the Devonian.

Vertebrate subphylum of chordates

Vertebrates comprise all species of animals within the subphylum Vertebrata. Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 69,276 species described. Vertebrates include the jawless fishes and jawed vertebrates, which include the cartilaginous fishes and the bony fishes.

Contents

Anatomy

Like their descendants, the pteraspidids, all cyathaspidiform heterostracans had the cephalothorax enclosed in armor, formed from several plates, including dorsal, ventral, a dorsal spine derived from a scale, and a large, scale-covered tail. Thus, the living animals would have resembled tadpoles encased in massive armor. The majority of taxa have the rostral and pineal plates fused or merged with the dorsal plate, and in the amphiaspidids, all the plates of the cephalothorax were fused together into a single "muff-like" unit. Unlike the pteraspidids, all cyathaspidiforms are thought to be almost uniformly benthic in lifestyle, though only the amphiaspids and the ctenaspids are thought to be burrowers.

Pteraspidiformes order of fishes (fossil)

Pteraspidiformes is an extinct order of heterostracan agnathan vertebrates known from extensive fossil remains primarily from Early Devonian strata of Europe and North America, and from Upper Silurian Canada.

Rostrum (anatomy) anatomical feature

In anatomy, the term rostrum is used for a number of phylogenetically unrelated structures in different groups of animals.

Pineal gland small endocrine gland found in most vertebrates, which produces melatonin; in humans, located in the epithalamus, in a groove where the two halves of the thalamus join; its shape and size resembles a pine nut, after which it is named

The pineal gland is a small endocrine gland in the brain of animals with backbones. The pineal gland produces melatonin, a serotonin-derived hormone which modulates sleep patterns in both circadian and seasonal cycles. The shape of the gland resembles a pine cone from which it derived its name. The pineal gland is located in the epithalamus, near the center of the brain, between the two hemispheres, tucked in a groove where the two halves of the thalamus join. It is also called the conarium, kônarion or epiphysis cerebri. The pineal gland is included among a group of specialized neuroendocrine brain structures called the circumventricular organs.

Taxonomy

The taxonomy of Cyathaspidiformes is a convoluted affair, as taking into account of several of the various problematic heterostracan taxa which strongly or superficially resemble cyathaspidiforms, such as Cardipeltis, Traquairaspis , Corvaspis and Tolypelepidida, Cyathaspidiformes appears to be polyphyletic. Phylogenetic analyses suggest that the tolypelepidid genera, including Athenaegis , Asketaspis , and in particular, Tolypelepis , are the sister-taxa of cyathaspidiforms. [1]

<i>Cardipeltis</i> genus of fishes (fossil)

Cardipeltis is an extinct genus of heterostracan agnathan from marine strata of early Devonian of Utah, and Wyoming. Species of Cardipeltis superficially resemble those of cyathaspids in having a flattened body and indistinct head covered by a large, broad, guitar pick or heart-shaped dorsal shield, and a long, scaly tail. Unlike cyathaspids, which all have a single ventral plate, however, the ventral shield of Cardipeltis is a mosaic composed of large scales.

<i>Traquairaspis</i> genus of fishes (fossil)

Traquairaspis is a genus of extinct heterostracan agnathan fish known from the Silurian and Early Devonian periods. It is predominantly known from Late Silurian fluvial deposits from Wales and England: some species were also found in shallow water marine environment in Canada and North America.

Tolypelepidida order of fishes (fossil)

Tolypelepidida is an extinct order of heterostracan vertebrates. These armored jawless fish superficially resemble their relatives, the cyathaspids, though, researchers place the tolypelepids as a sister group to the cyathaspids and the pteraspidids. A recent study by Lundgren and Blom in 2013 implies that the order is paraphyletic, with the type genus, Tolypelepis, being the sister taxon of Cyathaspidiformes. The typical tolypelepid had a carapace formed from dorsal and ventral plates, and a scaly tail.

Even within the order, there is much debate about organizing the taxa. Until recently, there were several families within the suborder Cyathaspidida, including Cyathaspididae, Irregularaspididae, Anglaspididae, Poraspididae, etc. In a phylogenetic survey in 2013 by Lundgren and Blom, the various families and genera within Cyathaspidida are reorganized into three families, Cyathaspidae, Ctenaspidae, and Ariaspidae. [1] The suborder Amphiaspidida, traditionally thought of as the daughter or sister-taxon of Ctenaspididae/Ctenaspidae, was excluded from this particular survey, as, while the authors did not directly challenge this idea, they excluded Amphiaspidida from the survey, noting that that group was "extremely derived and virtually impossible" to be of any use to this survey. [1]

Cyathaspidida order of fishes (fossil)

Cyathaspidida is a taxon of extinct cyathaspidiform heterostracan agnathans whose fossils are found in Silurian to Lower Devonian marine strata of Europe and North America. In life, they are thought to be benthic animals that lived most of their lives either mostly buried in or resting directly on top of the substrate.

Ctenaspidae family of fishes (fossil)

Ctenaspidae is a family of extinct cyathaspidiform heterostracan agnathans in the suborder Cyathaspidida.

Taxa

Cyathaspidiformes is divided into two suborders, Cyathaspidida and Amphiaspidida. The former has the cephalothorax armor divided into several plates, while the latter have the cephalothorax armor fused into a single "muff-like" unit.

Cyathaspidida

Typical cyathaspidid heterostracans were fusiform or cigar-shaped animals. Their fossils are found in Silurian and early Devonian marine and marginal marine strata of North America, Europe, and the Ural Mountains. Kiangsuaspis , from Silurian Chinese marine strata, was originally thought to be a Chinese cyathaspidid, until it was then reappraised as a phyllocarid crustacean. Currently, the taxa of this suborder are divided into three families.

<i>Kiangsuaspis</i> genus of fishes

Kiangsuaspis nankingensis is an extinct phyllocarid crustaceans from Late Silurian China. It was originally described in 1962 by Kiang P'an as an incomplete ventral plate of a cyathaspidid heterostracan agnathan with a unique pattern of raised, sculptured tubercles that fuse together into anastomosing ridges. In 1984, Jiang P'an then reappraised it as a ceratiocaridid crustacean.

Cyathaspidae

Cyathaspidae encompasses the taxa of the families Cyathaspididae, Irregularaspididae, and Poraspididae.

Ariaspidae

Ariaspidae encompasses the taxa Ariaspis and the taxa formerly contained within Anglaspididae ( Anglaspis , Liliaspis and Paraliliaspis ).

Ariaspis is an extinct genus of cyathaspidiform heterostracan agnathan. Fossils are found in marine strata of Canada and Europe from the late Silurian period until its extinction during the Early Devonian. A new species, A. arctata, was described by David K. Elliott and Sandra Swift in 2010.

<i>Anglaspis</i> genus of fishes (fossil)

Anglaspis is an extinct genus of cyathaspidiform heterostracan agnathan. Fossils are found in marine strata of Europe, from the late Silurian period until genus' extinction during the Early Devonian. As with other cyathaspidiforms, individuals of Anglaspis had dorsal and ventral plates covering the forebody, gill pouches, and nasal openings that lay on the roof of the oral cavity.

<i>Liliaspis</i> genus of fishes (fossil)

Liliaspis philippovae is an extinct cyathaspidiform heterostracan agnathan from early Devonian marine strata of the Ural Mountains.

Ctenaspidae

Ctenaspidae encompasses the ctenaspids, ( Ctenaspis , Arctictenaspis and Zaphoctenaspis ), and the allocryptaspids ( Boothiaspis , Allocryptaspis and Alainaspis ). Boothiaspis, from the Boothia Peninsula, was originally described as a Canadian amphiaspidid.

Life reconstruction of Ctenaspis dentata Ctenaspis NT small.jpg
Life reconstruction of Ctenaspis dentata

Amphiaspidida

All the cyathaspidiforms of Suborder Amphiaspidida, sometimes treated as a distinct order "Amphiaspidiformes," are endemic to Lower Devonian marine strata of what is now the Taimyr Peninsula, Siberia, in what was once a series of hypersaline lagoons cut off from the ocean. In addition to having the plates of the cephalothorax armor fused together to form a muff-like unit shaped like a pot pie or a hot water bottle, all amphiaspidids had a simple, slit-shaped mouth, and reduced or no eyes. These adaptations suggest that the living animals were filter- or suspension-feeders that habitually buried themselves in the substrate.

Related Research Articles

Amphiaspidida taxon of fishes (fossil)

Amphiaspidida is a taxon of extinct cyathaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of Siberia near the Taimyr Peninsula. Some authorities treat it as a suborder of Cyathaspidiformes, while others treat it as an order in its own right as "Amphiaspidiformes." In life, they are thought to be benthic animals that lived most of their lives mostly buried in the sediment of a series of hypersaline lagoons. Amphiaspids are easily distinguished from other heterostracans in that all of the plates of the cephalothorax armor are fused into a single, muff-like unit, so that the forebody of the living animal would have looked like a potpie or a hot waterbottle with a pair of small, or degenerated eyes sometimes flanked by preorbital openings, a pair of branchial openings for exhaling, and a simple, slit-like, or tube-like mouth.

Amphiaspidoidei superfamily of fishes (fossil)

Amphiaspidoidei is a taxon of extinct amphiaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of Siberia near the Taimyr Peninsula. In life, the amphiaspidids of Amphiaspidoidei are thought to be benthic animals that lived most of their lives mostly buried in the sediment of a series of hypersaline lagoons. Amphiaspids are easily distinguished from other heterostracans in that all of the plates of the cephalothorax armor are fused into a single, muff-like unit, so that the forebody of the living animal would have looked like a potpie or a hot waterbottle with a pair of small, or degenerated eyes flanked by preorbital openings, a pair of branchial openings for exhaling, and a simple, slit-like mouth.

Hibernaspidoidei superfamily of fishes (fossil)

Hibernaspidoidei is a taxon of extinct amphiaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of Siberia near the Taimyr Peninsula. In life, hibernaspid amphiaspidids are thought to be benthic animals that lived most of their lives mostly buried in the sediment of a series of hypersaline lagoons. All amphiaspids are easily distinguished from other heterostracans in that all of the plates of the cephalothorax armor are fused into a single, muff-like unit, so that the forebody of the living animal would have looked like a potpie or a hot waterbottle with a pair of small, or degenerated eyes, a pair of branchial openings for exhaling, and, in the case of hibernaspids, a simple, slit-like mouth at the anterior end of a tube-like head.

Siberaspidoidei is a taxon of extinct amphiaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of Siberia near the Taimyr Peninsula. In life, siberaspids are thought to be benthic animals that lived most of their lives mostly buried in the sediment of a series of hypersaline lagoons. As with all amphiaspids, siberiaspids are easily distinguished from other heterostracans in that all of the plates of the cephalothorax armor are fused into a single, muff-like unit, so that the forebody of the living animal would have looked like a flattened potpie or a hot waterbottle with a pair of small, or degenerated eyes sometimes flanked by preorbital openings, a pair of branchial openings for exhaling, and a simple, slit-like, or tube-like mouth.

Amphiaspididae family of fishes (fossil)

Amphiaspididae is a family of extinct amphiaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of Siberia near the Taimyr Peninsula. In life, the amphiaspidids of Amphiaspididae are thought to be benthic animals that lived most of their lives mostly buried in the sediment of a series of hypersaline lagoons. Amphiaspids are easily distinguished from other heterostracans in that all of the plates of the cephalothorax armor are fused into a single, muff-like unit, so that the forebody of the living animal would have looked like a potpie with a pair of small, or degenerated eyes, with each flanked by a preorbital opening, and a simple, slit-like mouth.

<i>Amphiaspis</i> genus of fishes (fossil)

Amphiaspis argo is the type species of the cyathaspidid taxon Amphiaspidida, and of the family Amphiaspididae. Its fossils are restricted to early Emsian-aged marine strata of the Taimyr Peninsula, Early Devonian Siberia. A. argo, as with all other amphiaspidids, is thought to have been a benthic filter feeder that lived on top of, or buried just below the surface of the substrate of hypersaline lagoon-bottoms.

Edaphaspis bystrowi is an extinct amphiaspidid cyathaspidid heterostracan. Its fossils are restricted to early Devonian-aged marine strata of the Taimyr Peninsula, Early Devonian Siberia. E. bystrowi, as with all other amphiaspidids, is thought to have been a benthic filter feeder that lived on top of, or buried just below the surface of the substrate of hypersaline lagoon-bottoms. It is the only representative of the family Edaphaspididae.

Gabreyaspididae family of fishes (fossil)

Gabreyaspididae is a family of extinct amphiaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of Siberia near the Taimyr Peninsula. In life, all amphiaspidids are thought to be benthic animals that lived most of their lives mostly buried in the sediment of a series of hypersaline lagoons. Amphiaspids are easily distinguished from other heterostracans in that all of the plates of the cephalothoracic armor are fused into a single, muff-like unit, so that the forebody of the living animal would have looked, in the case of gabreyaspidids, vaguely like a horseshoe crab with a pair of small, or degenerated eyes, with each flanked by a preorbital opening, and a simple, slit-like mouth positioned slightly ventrally.

Olbiaspididae family of fishes (fossil)

Olbiaspididae is a family of extinct amphiaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of Siberia near the Taimyr Peninsula. In life, all amphiaspidids are thought to be benthic animals that lived most of their lives mostly buried in the sediment of a series of hypersaline lagoons. Amphiaspids are easily distinguished from other heterostracans in that all of the plates of the cephalothoracic armor are fused into a single, muff-like unit, so that the forebody of the living animal would have looked, in the case of olbiaspidids, vaguely like a hot water bottle with a pair of small, or degenerated eyes, with each flanked by a preorbital opening, and a simple, slit-like mouth positioned at the anteriormost portion of the cephalothoracic armor.

<i>Hibernaspis</i> genus of fishes (fossil)

Hibernaspis is a genus of extinct amphiaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of Siberia near the Taimyr Peninsula. In life, species of Hibernaspis were thought to be benthic animals that lived most of their lives mostly buried in the sediment of a series of hypersaline lagoons. All amphiaspids are easily distinguished from other heterostracans in that all of the plates of the cephalothorax armor are fused into a single, muff-like unit, so that, in the case of Hibernaspis, the forebody of the living animal would have looked like a large guitar pic with serrated edges, with a pair of tiny, degenerated eyes, a pair of branchial openings for exhaling, and a simple, slit-like mouth at the anterior end.

<i>Paraliliaspis</i> genus of fishes (fossil)

Paraliliaspis egregia is an extinct cyathaspidiform heterostracan agnathan from early Devonian marine strata of the Ural Mountains.

Eglonaspididae is a family of extinct amphiaspidid heterostracan agnathans whose fossils are restricted to Lower Devonian marine strata of Siberia near the Taimyr Peninsula. In life, all of the amphiaspidids are thought to be benthic animals that lived most of their lives mostly buried in the sediment of a series of hypersaline lagoons. Amphiaspids are easily distinguished from other heterostracans in that all of the plates of the cephalothoracic armor are fused into a single, muff-like unit, so that the forebody of the living animal would have looked, in the case of elgonaspidids, very much like a hot water bottle with or without a pair of small, degenerated eyes and a simple, slit-like mouth positioned at the anteriormost portion of the cephalothoracic armor.

Ariaspidae family of fishes (fossil)

Ariaspidae is a family of extinct cyathaspidiform heterostracan agnathans in the suborder Cyathaspidida.

References

  1. 1 2 3 Lundgren, Mette, and Henning Blom. "Phylogenetic relationships of the cyathaspidids (Heterostraci)." GFF 135.1 (2013): 74-84.


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