Kingdom Animalia Family †Liwiidae Species †B. forteyi Order Nektaspida | Stem group Chelicerata Genus †Buenaspis
Budd, 1999 Phylum Arthropoda | |
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Similar Tariccoia, Aaveqaspis, Buenellus, Kleptothule, Naraoiidae | ||
Buenaspis is a genus of small (between 1 centimetre (0.39 in) and 3 centimetres (1.2 in) long) marine arthropods in the Liwiidae Family, that lived during the early Cambrian period. Fossil remains of Buenaspis were collected from the Lower Cambrian Sirius Passet Lagerstätte of North Greenland. Buenaspis looks like a soft eyeless trilobite. It has a headshield (or cephalon) slightly larger than the tailshield (pygidium), and in between them six thoracic body segments (somites). The genus is monotypic, its sole species being Buenaspis forteyi.
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Etymology
The name of the genus is from Buen Formation, the deposit where the species was collected, and the Greek word aspis (shield). The species was named in honor of Richard Fortey, a famed paleontologist.
Description
Buenaspis forteyi is between 1 and 3 cm along the axis, approximately half a wide as long, in general outline shaped as a bar with parallel sides and rounded front and back ends. It is likely the animal was distinctly convex, considering the many concentric crush-marks found in many specimens. The dorsal exoskeleton consists of a cephalon, a pygidium and six thoracic somites with articulating half-rings, all non-calcified. The cephalon is sub-semicircular, broader than it is long, and with rounded genal angles. Eyes are absent. Antennas are not known. The six thoracic somites are extended into broad posteriorly directed pleural spines, which are free at their tips. The caudal shield is slightly smaller than the cephalic shield, and somewhat more rounded. Some specimens appear to have a lengthwise mid-ridge from the cephalon to the pygidium. Although Budd attributes this feature to deformations, since it does not occur in all specimens known, later authors seem to have accepted it as authentic.
Differences with other Liwiidae
Distribution
B. forteyi has been collected from the Lower Cambrian (Atdabanian) Buen Formation, Sirius Passet Lagerstätte, Peary Land, North Greenland, on the south side of the broad valley known as Sirius Passet at its junction with J.P. Koch Fjord 82°47′6″N 42°13′7″W.
Habitat
Buenaspis forteyi was probably a marine bottom dweller, that lived in deeper water. This may be deduced from the dominance of eyeless forms and the absence of seaweeds at the collection site.
Taxonomy
The author that originally described Buenaspis and subsequent publications classified the genus as part of the Liwiidae family. Recently however, Paterson et al. propose to remove Buenaspis from the Nektaspida order entirely, on the argumentation that it lacks the 'waist' that is a common feature in Liwia, Soomaspis, Tariccoia, Misszhouia, Pseudonaraoia and Naraoia. Also, they regard the ridge on cephalon and pygidium in Buenaspis an artifact, unlike the ridge on the pygidium only in Soomaspis and Tariccoia. If Paterson et al. is followed, Buenaspis attains a position somewhere else in the Lamellipedia.