Dentition of the Southern Thorny Skate, Amblyraja doellojuradoi (Pozzi, 1935): Qualitative Analysis And Anomalies

DELPIANI, GABRIELA; MABRAGAÑA, EZEQUIEL; FIGUEROA, DANIEL E.

Montreal, Canadá

Congreso; Joint Meeting of Ichthyologists and Herpetologists; 2008

Dentition analysis of cartilaginous fishes is an important tool for determining species, establishing phylogenetic relationships between extinct and living taxa, and describing ontogenetic morphological changes. This work constitutes the first description of Amblyraja doellojuradoi`s dentition. The jaws (n = 72) were extracted, cleaned and prepared with two different treatments. Some of them were dried and whitened with 30% diluted hydrogen peroxide; while the tooth plates of others were taken and pasted on a vegetal paper. In the Southern thorny skate the dentition was gradient monognathic heterodonty. In the upper jaw, the symphysial teeth and approximately the two rows on both sides of them have low cusps, but their size increases in lateral teeth and reduce again in the commissural teeth. In the lower jaw, the cusps from the symphysial teeth are larger and arched, reducing their size to the commissural teeth. A. doellojuradoi presented ontogenetic heterodonty, having the juvenils cusps with little development, while adults have too much developed and sharp-pointed cusps. This ontogenetic change was manifest both in males and females, although in the first one was more conspicuous. Two kind of anomalies were observed in some specimens: (1) an additional incomplete row between two complete rows, and (2) an increasing tooth base size and division of their cusp until the tooth divided completely in the same row.  Gradient monognathic heterodonty as well as ontogenetic heterodonty is common in skates´ dentition. Indistinct sexual heterodonty observed in A. doellojuradoi was also recorded in A. radiata and Dipturus batis whereas other species exhibit marked sexual heterodonty or absence of heterodonty. Regarding anomalies in tooth arrangement, this is the first record of that kind of malformation in skates´ dentition.