How many extant pinniped species remain to be described?

Abstract

Large extant marine vertebrates continue to be discovered and described: during the late twentieth and early twenty-first century, several cetaceans and chondrichthyans exceeding three metres in total length have been described, including the megamouth shark, Omura's whale, Bandolero (or Peruvian or Lesser) beaked whale, and Perrin's beaked whale. Statistical methods have been employed by several workers in an effort to estimate the number of such species that remain to be described, and results indicate that between 10 and c. 50 such species remain. Here, we examine the description record of the pinnipeds using non-linear and logistic regression models in an effort to determine how many members of this group might remain undescribed. Regression based on a Michaelis–Menten function suggests that as many as 15 such species remain, whilst logistic regression suggests a far lower number (closer to 0). We combine these approaches with an evaluation of cryptozoological data, as ethnozoological evidence suggests the existence of several large-bodied marine vertebrates that have been interpreted by some authors as unusual pinnipeds. These include the so called ‘long-necked sea-serpent’, ‘merhorse’ and ‘tizhurek’. Because cryptozoological data are mostly discussed in the ‘grey literature’, appraisals of these cryptids have never appeared in the mainstream literature, perpetuating a cycle whereby these putative animals remain unevaluated.