How many sharks now?

Checklist of Living Sharks(Revised 1 January 2007)suchlist exists and, with the best of current data, it is not possible toconstruct such a list with any certainty.

I am reasonably confident about the arrangementwithin the Squalea and most of the Galea, except for parts of the orderCarcharhiniformes. A few of the more problematical areas are:

the large deep-sea genus Apristurus(family Scyliorhinidae) is in dire need of systematic revision (theremay be as many as 48 valid species or as few as 25),

placement of Scoliodon remains uncertain (it is clearly alliedwith Rhizoprionodon and the hammerheads, family Sphyrnidae, butexactly how this poorly-known shark is related is difficult todetermine),placement of Isogomphodon and Triaenodon are difficultbecause each of these monotypic genera feature a very odd combination ofcharacters, andthe family Carcharhinidae (as listed here) is perhaps the most complexand contentious group, especially those traditionally lumped within thegenus Carcharhinus. If Prionace and Negaprion arevalid genera, Carcharhinus is clearly polyphyletic. But how thatgenus should be sub-divided remains an open question which I ampresently investigating with a colleague, geneticist Mahmood Shivji, ofNova Southeastern University.

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