Bairdops
| Bairdops Temporal range:
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|---|---|
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Malacostraca |
| Order: | Stomatopoda |
| Family: | †Perimecturidae |
| Genus: | †Bairdops Schram, 1979 |
| Type species | |
| †Perimecturus elegans Peach, 1908
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| Species | |
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| Synonyms | |
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synonyms of B. elegans
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Bairdops is an extinct genus of mantis shrimp that lived during the Carboniferous period in what is now Scotland and the United States. It contains two named species. The type species, B. elegans, was described in 1908 by Ben Peach as a species of Perimecturus, and fossils of it are known from Scotland. A second species, B. beargulchensis, was named from specimens found in the Bear Gulch Limestone of Montana.
Discovery and naming
The fossilized remains of Bairdops have been discovered decades prior to the establishment of the genus. In 1908, Ben Peach became the first to study specimens of this animal, which were collected in Scotland by A. Macconochie. However, Peach believed they represented members of Perimecturus, another genus of early stomatopods. He erected the species Perimecturus elegans based on remains found near the River Esk in Glencartholm. In addition, he also erected the species Perimecturus ensifer from fossils found in Liddel Water, Newcastleton and Glencartholm.[1]
In 1979, Frederick Schram found that P. elegans and P. ensifer were indistinguishable from each other, thus the latter was declared as a junior synonym of the former. He also noted that the tail fan, body shape and size of this species differed significantly from what is seen in other species of Perimecturus. Schram therefore erected the genus Bairdops with P. elegans as the type species, which was subsequently renamed as Bairdops elegans, and the specimen GSE 5879 was designated as the lectotype of this species. The generic name honors William Baird, the Assistant Curator of the fossil invertebrate collection at the Royal Scottish museum.[2]
Additionally, Schram described a second species of Bairdops in 1978 which he named B. beargulchensis. The specific name refers to the Bear Gulch Limestone in Fergus County, Montana, where the holotype (UM 6217) was collected.[3] Although Factor and Feldman (1985) declared this species to be a junior synonym of Tyrannophontes theridion, a later study by Jenner et al. (1997) found that B. beargulchensis is most similar to B. elegans, thus revalidating B. beargulchensis.[4][5]
Description
Bairdops is a crustacean of moderate size, with B. elegans having a carapace length of 0.76–2.93 cm (0.30–1.15 in) and a total abdomen length of 1.50–5.03 cm (0.59–1.98 in).[2] B. beargulchensis is slightly larger and more robust, with a carapace ranging from 1.75–2.67 cm (0.69–1.05 in) and a total abdomen length of 1.60–5.20 cm (0.63–2.05 in).[3]
The rostrum is about a third the length of the carapace and is spatula-like in shape, with a tapering, pointed tip and a wide base. The antennae are not well preserved, but it is known the scaphocerite (exopod of the antenna) is very large. A pair of large and circular compound eyes are present on the head. The large, elongated carapace covers the entire thorax in B. elegans, whereas in B. beargulchensis it leaves only the top of the eighth thorax segment exposed. The carapace has a subrectangular shape and a furrow on its edges. This furrow is prominent in B. elegans but very slight in B. beargulchensis.[3] The back margin of the carapace is concave at the top, with its sides extending slightly further and reaching the front of the first abdominal segment.[5]
Pairs of raptorial appendages are attached to the thorax, though it is unclear whether there are four or five pairs of these. The coxae, ischiomeri and carpi of these appendages are short, whereas the propodi (penultimate segment) and dactyli (final segment) are longer. The longest segment of a raptorial appendage in Bairdops is the basis. Though Schram and Horner (1978) claimed the propodi of B. beargulchensis possessed two rows of spines, this observation was based on specimens now reassigned to Daidal acanthocercus.[3][5] Propodus spines are currently believed to only be present in B. elegans.[6]
All thoracic segments are shorter than the abdominal segments. The thoracic segments further front possess narrow sternites and are smaller than the sixth to eighth thoracic segments. The abdominal segments decrease in both height and width down the animal's length, and their side margins are rather straight. Moderate furrows are present on the lower margins of each abdominal segment. In B. beargulchensis, the fifth and sixth abdominal segments may possess one or two backward-pointing ridges extending past the back margin of their respective segments.[5]
References
- ^ Peach, B. N. (1908). Monograph on the higher Crustacea of the Carboniferous rocks of Scotland. Glasgow: Printed for H.M. Stationery off., by J. Hedderwick & sons, ltd.
- ^ a b Schram, Frederick R.; Schram, Frederick R. (1979). British Carboniferous Malacostraca. Chicago: Field Museum of Natural History.
- ^ a b c d Schram, Frederick R.; Horner, John (1978). "Crustacea of the Mississippian Bear Gulch Limestone of Central Montana". Journal of Paleontology. 52 (2): 394–406. ISSN 0022-3360.
- ^ Factor, D.F.; Feldman, R.M. (1985). "Systematics and paleoecology of malacostracan arthropods in the Bear Gulch Limestone (Namurian) of central Montana USA". Annals of Carnegie Museum. 54 (10): 319–356.
- ^ a b c d Jenner, Ronald A.; Hof, Cees H. J.; Schram, Frederick R. (1998). "Palaeo- and archaeostomatopods (Hoplocarida, Crustacea) from the Bear Gulch Limestone, Mississippian (Namurian), of central Montana". Contributions to Zoology. 67 (3): 155–185. ISSN 1383-4517.
- ^ Briggs, D. E. G.; Clarkson, E. N. K. (1985). "Malacostracan Crustacea from the Dinantian of Foulden, Berwickshire, Scotland". Earth and Environmental Science Transactions of The Royal Society of Edinburgh. 76 (1): 35–40. doi:10.1017/S0263593300010270. ISSN 1473-7116.