Tourist attacked by Shark off Florida Keys.

A tourist has been attacked by a Shark while snorkeling in the Florida Keys on the morning of Sunday 20 September 2020, according to the Monroe County Sheriff's Office. Charles Eddy, 30, was bitten on the shoulder by a 2.8-3.0 m Shark shortly after entering the water from a vessel close to Sombrero Key Light, offshore of Vaca Key. He received what have been described as 'severe' injuries, and was airlifted to the Ryder Trauma Center in Maimi. The Shark is believed to have been a Bull Shark, Carcharhinus leucas, a species noted for its aggresive behaviour, as several boaters had reported seeing a similar-sized member of this species in the area shortly before the attack.

 

A Bull Shark, Carcharhinus leucas, in the Bahamas. Albert Kok/Wikimedia Commons.

Despite their fearsome reputation, attacks by Sharks are relatively rare. Most attacks on Humans by Sharks are thought to be mistakes, made by species that feed principally on Marine Mammals (which we superficially resemble when we enter the water), gaining the majority of their nutrition from the thick adipose (fat) layers of these animals (which we lack). Due to this, when Sharks do attack Humans these attacks are often broken off without the victim being consumed. Such attacks frequently result in severe injuries, but are seldom immediately fatal, with victims likely to survive if they receive immediate medical attention.

Bull Sharks, Carcharhinus leucas, are a form of Requiem Shark, Carcharhinidae, reaching about four metres in length at their largest. They have a reputation for aggressive behaviour, and are one of the species most prone to attacking Humans, though this is not because they are more hostile towards us than other Shark species, but because they inhabit environments where they are more likely to encounter us, favouring shallow inshore waters, and sometimes entering freshwater systems, which most Sharks shun (Bull Sharks have been encountered in the Mississippi River as far inland as southern Illinois). These Sharks are also territorial, and may lash out if they feel their territory is being invaded.

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Diprosopovenator hilperti: A new species of Ground Shark from the Late Cretaceous of Lower Saxony, Germany.

The Ground Sharks, Carcharhiniformes, are the largest extant Shark group today, comprising over 280 species, which are variously refereed to as Requiem Sharks, Weasel Sharks, Houndsharks, Catsharks and Hammerheads. They have a fossil record which dates back to the Middle Jurassic, though, as with other Shark groups, this comprises almost entirely of teeth, due to the lack of a mineralised skeleton. 

In a paper published in the Journal of Vertebrate Paleontology on 3 May 2019, Sebastian Stumpf of the Department of Palaeontology at the University of Vienna, Udo Scheer of Sat Mătăsaru in Romania, and Jürgen Kriwet, also of the Department of Palaeontology at the University of Vienna, describe a new species of Ground Shark from the Late Cretaceous Hesseltal Formation of Lower Saxony in northeast Germany.

The Hesseltal Formation comprises a sequence of organic-rich laminated marlstones with organic carbon alternating with light and sometimes red limestone and marl beds, associated with a time of rapid global warming, rising sea levels and repeated incidents of ocean anoxia, known as the Cenomanian–early Turonian Oceanic Anoxic Event 2.

The new species is named Diprosopovenator hilperti, where 'Diprosopovenator' means 'two-faced hunter', in reference to the fact that the specimen is preserved in two slabs as part and counterpart, and 'hilperti' honours fossil collector Karl-Heinz Hilpert, who found rhe specimen from which the species is described and donated it to the Ruhr Museum in Essen. One of the slabs preserves part of the neuro- and splanchocranium, including part of the upper and lower mandibular arch with associated dentition, as well as a patch of densely packed placoid scales posterior to the cranium, the other remains of the lower mandibular arch plus associated dentition, part of the anterior vertebral column comprising nine vertebral centra, as well as part of the dermis. All are somewhat compressed and distorted.

Diprosopovenator hilperti, RE A 4872/1, holotype. (A) interpretative composite drawing combining RE A 4872/1 (dark gray) and RE A 4872/2 (light gray). (B)–(E), RE A 4872/1. (B), under normal light; (C), close-up view of placoid scales; (D), interpretative drawing; (E), under ultraviolet light. Abbreviations: ao.w, antorbital wall; d, dermis; hym, hyomandibula; l, left (in parentheses, e.g., ‘M.c(l)’); M.c, Meckel’s cartilage; nc, neurocranium; ot.cap, otic capsule; pl.sc; placoid scales; po.pr, postorbital process; po.w, postorbital wall; pq, palatoquadrate; r, right (in parentheses, e.g., ‘M.c(r)’); so.cr, supraorbital crest; spt.r, sphenopterotic ridge; t, teeth; v.c, vertebral centra. Stumf et al. (2019).

The teeth of Diprosopovenator hilperti resemble those of modern Catsharks, Scyliorhinidae, a group currently considered to date back to the Middle Jurassic. However recent mollecular studies have suggested that the Scyliorhinidae is a paraphyletic group (i.e. does not contain all the descendents of their most recent common acestot), which makes the inclusion of ancient fossils in the group difficult, for which reason Stumf et al. recomend that all fossil species currently assigned to the Scyliorhinidae, should be considered to be unplaced members of the Carcharhiniformes until they are better understood. Having said this, they note that Diprosopovenator hilperti does appear to be closely related to the previously desctibed Pseudoscyliorhinus reussi  and Pseudoscyliorhinus schwarzhansi, and therefore place the three species together in a new family, the Pseudoscyliorhinidae.

Diprosopovenator hilperti, RE A 4872/2, holotype, (A) under normal light; B, close-up view of vertebral column; (C) under ultraviolet light. Abbreviations: l, left (in parentheses); M.c, Meckel’s cartilage; r, right (in parentheses). Stumf et al. (2019).

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