Birkenia elegans TRAQUAIR, 1899

Taxonomy

Anaspid

Kingdom: Animalia
Phylum: Chordata
Class: Anaspida Traquair, 1899
Order: Birkeniida Berg, 1937
Family: Birkeniidae Traquair, 1899
Genus: Birkenia
Species: Birkenia elegans
Author Citation TRAQUAIR, 1899

Geological Time Scale

Eon: Phanerozoic
Era: Paleozoic
Period: Silurian
Sub Period: None
Epoch: Wenlock
International Age: Sheinwoodian

Stratigraphy

Waterhead Group
Slot Burn Formation

Provenance

Collector: T. Bastelberger
Date Collected: 06/01/1970
Acquired by: Field Collection

Dimensions

Length: 3 cm

Location

Slot Burn
Lesmahagow
Scotland
United Kingdom

• anaspid
• birkenia
• lesmahagow
• scotland
• silurian
• slot burn
• tff-oilshale-ch770
• wenlock

Comments

Many important collections of Silurian arthropods and vertebrates have been made near Lesmahagow since the mid to late 1800's. The Lesmahagow Inlier is a block of Silurian sediments surrounded by sediments of Carboniferous age. The inlier consists of shales and sandstones with occasional pebble conglomerates of a lagoon or lake. This fish is from Slot Burn SSSI (Site of Special Scientific Interest), now off-limits to all collecting due to overzealous collecting.

Taxonomy from Blom et al. 2002.

Diagnosis for Birkenia elegans from Blom et. al 2002, p. 277: "Small species of Birkenia, up to 10 cm long, with double-headed mid-dorsal spine; dorso-lateral scales inclined to the anterior anteriorly and to the posterior posteriorly; whole body covered with similar, regular granular to finely tuberculate sculpture; mid-part of lateral scales, double- headed dorsal spine and scales on anal fin, showing regular dorso-ventral arrangement of sculpture; lateral scales towards articulation sockets show similar regular but not linearly arranged sculpture as do all ventral and dorsal plates, and rostral and pineal plates of the head; sculpture in anterior- posterior arrangement on pineal plates and postbranchial spine."

 The Anaspida were small marine agnathans (Greek, "no jaws") that lacked paired fins and often scales. They first appeared in the early Silurian and flourished until the late Devonian. Birkenia was a derived form of anapsid that grew to a maximum length of about 10cm. The Anaspids were simple dorso-laterally compressed fish that probably led a bottom-dwelling existence. It was adapted for active swimming and had a sucking mouth that was terminal rather than ventral. Birkenia has a characteristic row of anterior and posterior pointing dorsal scales. The gills opened as a row of holes along the side of the animal, typically numbering from 6-15. The tail is hypocercal which means that the lower lob is the longest. Traquair reconstructed Birkenia upside down because he never met this condition in a fish before.

Line drawing from Stetson 1928, p. 468:

    

Identified by oilshale.    

References:

D.L. Dineley: British fossil fish and amphibian sites, Chapter 1
GRC site account Slot Burn
GRC site account Birk Knowes
GRC site account Birkenhead Burn
Stetson, Henry C. (1928) A Restoration of the Anaspid Birkenia elegans Traquair. The Journal of Geology, Vol. 36, No. 5, pp. 458-470.
Blom, H., Märss, T. and Miller, C. G. (2002) Silurian and earliest Devonian birkeniid anaspids from the Northern Hemisphere. Transactions of the Royal Society of Edinburgh: Earth Sciences, 92, 263-323, (for 2001).
Blom, Henning. "New birkeniid anaspid from the Lower Devonian of Scotland and its phylogenetic implications." Palaeontology 55.3 (2012): 641-652.