A megamouth shark (Lamniformes: Megachasmidae) in the Burdigalian of Belgium

Abstract

The enigmatic megamouth shark is a rare occurrence in both Recent oceans and in the fossil record. A temporary construction site in the city of Antwerp (NW Belgium) gave the opportunity to study the poorly known early Miocene Kiel Sand Member of the Berchem Formation. In this Burdigalian deposit, a previously unknown fossiliferous horizon with Glycymeris and Cyrtodaria was sampled which contained a single Megachasma tooth. This specimen, attributed to Megachasma aff. pelagios by its resemblance with extant M. pelagios, is the first in situ record from un-reworked strata in Belgium. Only around a dozen fossil Megachasma teeth have been reported from Europe. It is concluded that a circumglobal megamouth population existed during the Burdigalian. Some evolutionary remarks are made.

Distinguishing the Miocene Kiel and Antwerpen Members (Berchem Formation) and their characteristic horizons using cone penetration tests in Antwerp (northern Belgium)

“…A closer look at the correlation between the Argenta outcrop as described and drawn by De Schutter and Everaert (2020) and a nearby mechanical CPT. Everaert et al (2020) performed dinocyst analyses on samples of this outcrop and thereby established the biozones as defined by de Verteuil and Norris (1996), shown on the right‐hand side.…”

“…According to Louwye et al (2000), this level represents the top of the early‐middle Burdigalian dinocyst biozone DN2 in this section. The overlying higher parts (6 m) of the Kiel Member were attributed to the late Burdigalian zone DN3. Z2: In the Argenta and Tweelingenstraat outcrops, about 2.5 m below the top of the Kiel Member, another (1–15 cm thick) calcareous, glauconitic sandstone level was described by De Schutter and Everaert (2020) and Everaert et al (2020). Especially at the Argenta outcrop, this sandstone bed, with short interruptions, was often massive and contained a thanatocoenosis of worn Glycymeris in its top surface (Figure 8b,c).…”

“…A total of seven outcrops was selected along a more or less S‐N line to the east of the city of Antwerp. These outcrops include some older sections exposed in the 1960s during the construction of the Antwerp Ring Road (De Meuter et al, 1976; Berchem‐Grote Steenweg, Borgerhout‐Stenen Brug and Borgerhout‐Rivierenhof), and more recent temporary outcrops described by Louwye et al (2010; Posthofbrug), Everaert et al (2019; Post X), De Schutter and Everaert (2020; Argenta) and Everaert et al (2020; Tweelingenstraat and a synthesis of the Argenta and Post X sections).…”

“…In the central and northern Antwerp city area, the Kiel Member is covered by the fossiliferous Antwerpen Member. In several temporary outcrops in and around the city of Antwerp, the boundary between the Antwerpen and Kiel Members was described in great detail and illustrated by De Meuter et al (1976), Louwye, Marquet, Bosselaers, and Lambert (2010), Hoedemakers and Dufraing (2018), De Schutter and Everaert (2020) and Everaert et al (2019, 2020). The latter authors indicated that the Antwerpen Member appears finer grained and more clayey in the basal parts compared to the underlying Kiel Member.…”

“…The central Kiel Member forms a particular unit of the Berchem Formation, as its rather coarse sands often lack fossils due to strong decalcification in its type area, southern Antwerp (De Meuter & Laga, 1976). Recent studies have, however, shown that the Kiel Sands contain some (fragile) shell beds to the north of the city (De Schutter & Everaert, 2020; Everaert et al, 2020). In the central and northern Antwerp city area, the Kiel Member is covered by the fossiliferous Antwerpen Member.…”