New evidence indicates the presence of barracuda (Sphyraenidae) and supports a tropical marine environment in the Miocene of Madagascar.

Michael D Gottfried,Summer A Ostrowski,Karen E Samonds,Tolotra Niaina Ramihangihajason,Tsiory Harimalala Andrianavalona,Geerat J Vermeij

doi:10.1371/journal.pone.0176553

Abstract

Recent exploration of Miocene-age deposits at Nosy Makamby, a small island ~50 km southwest of Mahajanga city in northwestern Madagascar, has led to the recovery of a large sample [82] of isolated barracuda teeth (Sphyraena sp.). in a tropical marine fauna that also includes diverse marine invertebrates, chondrichthyans, bony fishes, turtles, crocodylians, and sirenians. Characteristically for barracudas, the teeth are labiolingually flattened and fang-like with a broadly triangular and blade-like acuminate outline and sharply edged but unserrated cutting margins. These barracudas inhabited an environment that included coral reefs (based on fossil scleractinians) and seagrass beds (evidenced by the epiphytic benthic foraminifera Elphidium sp.). The relatively common occurrence of Miocene barracuda at Nosy Makamby corroborates the presence of a tropical marine ecosystem encircling Madagascar by the Miocene, likely similar overall to the environment found there today.

Highlights

Madagascar is perhaps the leading example of a ‘biodiversity hotspot’ owing to the exceptionally high rates of endemism seen in its native biota [1,2,3], and as such the deep-time evolutionary history of the island’s unique flora and fauna has long been of interest [4,5,6,7,8]
Field expeditions exploring a range of Mesozoic sites on the island have discovered some remarkable and highly informative fossils [9,10,11,12,13,14,15,16]; the Mesozoic finds are, unlikely to represent direct ancestors or very close relatives of the endemic forms that live on the island today
No jaw or other bony skeletal elements clearly attributable to barracudas have been recovered from Nosy Makamby, but the collection of teeth taken as a whole is diagnostic for the presence of Sphyraena and strong evidence that barracuda were common in the Miocene marine ecosystem on the western side of Madagascar

Summary

Introduction

Madagascar is perhaps the leading example of a ‘biodiversity hotspot’ owing to the exceptionally high rates of endemism seen in its native biota [1,2,3], and as such the deep-time evolutionary history of the island’s unique flora and fauna has long been of interest [4,5,6,7,8]. Andrianavalona et al [19] recently described the Miocene shark and batoid fauna from Nosy Makamby, which includes 10 taxa of chondrichthyans, six of which were previously unreported from Madagascar. These inhabited a nearshore environment that contained corals, bivalves, gastropods, bony fishes, turtles, crocodylians, and sirenians. Sphyraenids are acanthomorph teleosts traditionally placed within the scombroids (mackerels and allies) They are widely distributed as fossils during the Cenozoic, in tropical to subtropical latitudes in the Atlantic Basin (see Fig 4). Betancur-R. et al [28] placed Sphyraenidae as incertae sedis in their Subseries Carangimorphariae, and we follow that classification here

Materials and methods

Discussion