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Megalops atlanticus (tarpon) vertebra from the Calvert Formation, VA

Megalopidae family (Jordan & Gilbert, 1882)

The Tarpon


Tarpon Info Fossil Morphology Associated Find Tarpon Fossil Examples

Information

According to most literature, including The Taxonomicon and Mikko’s Phylogeny Archive, the earliest occurrence of the megalopidae family appears in the Cretaceous of Europe. There are five genera included in this family. They are:

Elopoides in lower Cretaceous of Europe
Sedenhorstia in upper Cretaceous of Europe
Protarpon in lower Eocene of Europe
Promegalops in lower Eocene of Europe
Megalops in Miocene to recent


Today there is one living genera of tarpon, megalops. Megalops most likely originates in the Miocene, as no publications of the occurrence of these genera before the Miocene could be found when writing this article.

Today, there are two species of megalops, one Atlantic species, and one Pacific species. The Pacific species is called megalops cyprinoides, and the Atlantic species is called megalops atlanticus.
Both species live in near shore environments and live both in salt and brackish waters. According to the FMNH tarpon have a modified air bladder that allows them to breathe air from the atmosphere and live in oxygen poor waters.
Extant tarpon are large fish. The Atlantic species can reach sizes of 250 cm, or 98 inches (marinebio.org), while the Pacific species can reach sizes of 150 cm, or 59 inches (Fishbase.org).

Fossil Morphology

The most common fossils of Tarpon appear to be their vertebra. The vertebrae superficially resemble a shark’s vertebra. As they both look like a shortened cylinder with a concave top and bottom. However, tarpon vertebrae seem to have a more oval shape than shark vertebrae. Also parts of the processes are usually still present on tarpon vertebrae, whereas shark vertebrae almost never have the processes attached.

The image below shows an example tarpon vertebra (megalops cf m. atlanticus) from the Miocene Calvert Formation of VA.

views of a fossil tarpon vertebra

An Associated Find

During the winter of 2009 I was fortunate enough to encounter associated fossils from a tarpon (megalops cf M. atlanticus). The specimen came from Shattuck's Zone 14 of the Calvert Formation in VA, which is Miocene in origin. It looked like the specimen was normally under water, however a very low tide had exposed the remains, which were now being battered by waves. Unfortunately it appeared most of the specimen had already eroded away. There were a few vertebrae left clinging to the matrix, and one washing in the waves. Also with the vertebra was a piece of bone, which appears to be skull material. Below are some images of the find.


picture of the associated tarpon find
This is the specimen as found.


Here is a closer view of the specimen.

seven associated tarpon fossil vertebra
This is the find after being prepped. I left one vertebra in the matrix for verification of the Zone.


Here are the side views of the vertebra. The side views of the vertebra in matrix cannot be shown.

The Fossils


megalops cf M atlanticus (Valenciennes, 1847), megalopidae gen. et sp. indet.



Megalops cf M. atlanticus
Atlantic Tarpon
Miocene to Recent

Identification note:
Attempting to identify teleost fauna (bony fish, not sharks) can be challenging from the Calvert Formation, as most publications discuss the shark, cetacean, or land mammal fauna. Fortunately, at Aurora, the Pungo River Units are based on Shattuck’s zones (Ward, p. 333) of the Calvert Formation. Also, since the cetacean fauna is remarkably similar to the cetaceans of the Calvert Formation (Whitmore and Kaltenbach, p. 257), and the shark fauna of each formation is nearly identical (pers. obs.), the teleost fauna is most likely also very similar. Therefore, I turned to Pungo River fossils for identification. After perusing the Lee Creek III book, Purdy et. al, described vertebrae from Pungo River units 5 and 6 that were nearly identical to the ones I found. The author said they closely resemble the vertebrae of the living tarpon, megalops atlanticus (Purdy et. al, p. 162), and therefore called them megalops cf M. atlanticus.
Click to view the fossils as found
These are seven associated vertebra and a fragment of skull from a Tarpon.
The fourth vertebra was left in matrix for verification of the Calvert Zone.

Formation: Calvert: Zone 14
Age: Early - Middle Miocene ~ 18-15 m.y.
Location: Chesapeake Bay Area
Size: Each vert is ~ 1.5" in diameter (38mm)
Date: November, 2009 TRIP
This is a vertebra from a Tarpon.
Purdy et al. indicate tarpon specimens come from the Pungo River Formation units 5 and 6 at the PCS mine in Aurora. (Purdy et al. 2001, p.162)

Formation: ?Pungo River
Age:Miocene ~15 m.y.o.
Location:PCS Mine, Aurora, NC
Size: the vert is ~ 1 1/4" in diameter (32mm)
Megalopidae genera et sp. indet.
Tarpon
Eocene
This is a fin spine fragment of fish from the Tarpon family. The genus is indeterminate.
This specimen comes from Muddy Creek, VA.
Weems (Weems et al, 1999, p56-57) states this is a fin ray fragment. Weems says it can be identified by as a member of the megaloptidae family because "it is composed of multiple segments that are strongly torqued" (p.57). This intense torquing is only seen in the megalopidae family. However, he states the genera cannot be narrowed down because there are two genera of tarpon that occur in the Eocene, Promegalops and Protarpon (p.57). Spine fragments cannot determine to which genera the fish belongs.

Formation: Nanjemoy Formation, Potapaco member, lower part of bed B, Fisher Lane Bone Bed
Age: Eocene: 56 m.y.
Location: Fisher Lane Bone Bed (Muddy Creek), VA
Size: ~ .9" tall (23mm)


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