Boii is an extinct genus of microsaur within the family Tuditanidae. It was found in Carboniferous coal from mines near the community of Kounov in the Czech Republic. The only remains of the genus consist of a crushed skull, shoulder girdle bones, and scales, which were similar to microsaurian elements originally referred to Asaphestera. Boii can be characterized by its heavily sculptured skull, thin ventral plate of the clavicles, and a larger number of fangs on the roof of the mouth. For many years the type and only known species, Boii crassidens, was considered to be a species of Sparodus, until 1966 when Robert Carroll assigned it to its own genus.
History
The specimen now designated as Boii crassidens was first described by Antonin Frič, one of the most notable paleontologists in the late 19th century region of Bohemia (now part of the Czech Republic). Frič made many contributions to knowledge of Carboniferous tetrapods during his lifetime, including a particular article published in "Sitzungsberichte der königlichen Böhmischen Gesellschaft der Wissenschaften in Prague", the most notable bohemian scientific journal of its day. The article, which was published in 1876 within volume 1875 of the journal, was a list of Carboniferous animals he and his associates recently discovered at gaskohle (bituminous coal) mines near the localities of Nýřany and Kounová. His list included short preliminary descriptions for many new genera and species of tetrapods, including Microbrachis, Branchiosaurus, Hyloplesion (at that time called Stelliosaurus), and Sparodus.
Most of the "Saurier" (reptiles, amphibians, or other tetrapods) he discussed in the article hailed from the Nýřany mines, with only two diagnostic examples found within the Kounová mines. One of these was a supposed amphibian he designated as "Labyrinthodon" shwarzenbergii, which is now known to not be an amphibian at all, but rather an early synapsid named Macromerion. The other specimen, which is now known as Boii crassidens, he named Batrachocephalus crassidens. This specimen consisted of a crushed skull, preserved on a slab and counterslab of coal. Jaw bones, scales, and shoulder girdle elements were preserved on the slabs as well. It is currently held at the National Museum in Prague, with the designation ČGH 83.
This article was only a preliminary review of the creatures Frič and his associates discovered. A more elaborate description was published in 1883 as part of a personal monograph focusing solely on the creatures discovered at these mines. This description renamed Batrachocephalus crassidens to Sparodus crassidens, as the genus name 'Batrachocephalus' was already taken by Batrachocephalus mino, an Indonesian species of catfish. Frič also assigned an isolated maxilla (upper jaw bone) with designation ČGH 124 to this species, although it was quite a bit larger than the maxilla of the crushed skull.
In a 1966 review of microsaurs published by Robert Carroll, "Sparodus" crassidens was not found to be a member of the genus Sparodus. Instead, it was re-evaluated as belonging to a family of early microsaurs known as the Tuditanidae. This prompted Carroll to create a new genus name for the specimens previously considered to belong to "Sparodus" crassidens. The new name he found was Boii crassidens, named after the Boii tribe which inhabited the area of Bohemia during the time of the Roman Republic.
Description
Skull
The crushed skull was pressed between two plates of coal which preserved the outer impressions of bones on both the underside and upper side of the specimen. Although not all of the bones were preserved, the outer impressions helped to reconstruct the structure of these missing bones. The impressions were used to reconstruct the skull and lower jaws, while the skull itself (which preserved the palate better than the impressions) was removed and encased in Canada balsam. The skull was initially believed to have been stout, approximately as long as it was wide. This 'frog-like' skull is responsible for the original genus name "Batrachocephalus", which is Greek for "frog head". However, later reconstructions from Robert Carroll have interpreted this wide shape as a result of the crushing the skull experienced, with the skull actually being narrow and somewhat triangular, more similar in shape to that of a lizard rather than a frog.