Chesapecten
Extinct scallop genus abundant in Mid-Atlantic Miocene to Pleistocene seas.
Chesapecten is an extinct scallop genus whose fossils appear in marine deposits spanning the early Miocene through the early Pleistocene along the Eastern United States. During that time, it thrived in the shallow seas of the Mid-Atlantic region. Although other scallops coexisted with it, Chesapecten was the most common.
The shells of Chesapecten, like those of several large scallops, have wide ribs that spread outward from the shell’s tip. A key trait is that these radial ribs are crossed by much finer, rough ribs that run parallel to the shell’s edges. The left valve is more curved than the right one, and the scar where the adductor muscle attached is large and round.
Geographically, Chesapecten is restricted to North America’s Atlantic coastal plain, ranging from Florida in the south to Delaware in the north. One species, *Chesapecten jeffersonius*, serves as Virginia’s state fossil.
Chesapecten holds the distinction of being the first North American fossil genus to be described and illustrated—a drawing of *C. jeffersonius* appeared in Martin Lister’s *Historiae Conchyliorum, Liber III* in 1687. However, Lister did not name it. The genus was formally named in 1975 by paleontologists Ward and Blackwater, and in 1980 Harold E. Vokes assigned it to the family Pectinidae. The name *Chesapecten* derives from the Chesapeake Bay, where eroding cliffs and outcrops along beaches regularly expose specimens.
Chesapecten lived on the seafloor in coastal waters from a few feet deep to about 130 feet. When stationary, it likely rested its flatter right valve on the seabed. Like nearly all living scallops, it probably could escape predators by suddenly flapping its valves and using the resulting jet propulsion.
Different species dominated at different times: *C. middlesexensis* during the Miocene (Eastover Formation); *C. jeffersonius* during the early Pliocene (Lower Yorktown Formation, roughly 4.5 to 4.3 million years ago); and *C. madisonius* during the late Pliocene (Upper Yorktown Formation, about 4 to 3 million years ago). Species in the genus include: *C. coccymelus*, *C. jeffersonius*, *C. madisonius*, *C. m. sarasotensis*, *C. marylandica*, *C. middlesexensis*, *C. m. bayshorensis*, *C. m. hunterae*, *C. monicae*, *C. nefrens*, *C. quinarius*, *C. santamaria*, *C. sayanus*, *C. septenarius*, and *C. skiptonensis*.
Quick Facts
- Taxon
- Chesapecten
- Type Species
- Chesapecten nefrens
- Type Species Authority
- Ward & Blackwater, 1975
Facts from the source article.
Lore & Background
The shells of Chesapecten are characterized by a pattern of wide ribs radiating from the apex, crossed by much smaller, rough, concentric ribs that follow the shell edges. The left valve is more convex than the right valve, and the adductor muscle scar is large and rounded. The name Chesapecten comes from the Chesapeake Bay, where eroding cliffs and outcrops along the beaches regularly expose specimens.
Chesapecten was the first genus of North American fossil to be described and illustrated; a drawing of C. jeffersonius appeared in English naturalist Martin Lister's Historiae Conchyliorum, Liber III in 1687. However, Lister did not give Chesapecten its name. It was formally named in 1975 by the paleontologists Ward and Blackwater, and in 1980 assigned to the family Pectinidae by Harold E. Vokes.
Chesapecten lived on the seabed in coastal waters ranging in depth from a few feet to 130 feet. When not moving, it is assumed to have rested its flatter right valve on the seafloor. It is very likely that Chesapecten could move suddenly to escape a predator by flapping its valves and using the resulting jet propulsion, similar to almost all living scallops.
Reader's Guide
Chesapecten holds significance as the first genus of North American fossil to be described and illustrated, with a drawing of C. jeffersonius appearing in Martin Lister's 1687 work. Its formal naming in 1975 by Ward and Blackwater, and later assignment to Pectinidae by Harold E. Vokes in 1980, established its taxonomic position. The genus is notable for its abundance in the shallow seas of the Mid-Atlantic during the early Miocene to early Pleistocene. Different species dominated during specific intervals: middlesexensis during the Miocene (Eastover Formation), jeffersonius during the Early Pliocene (Lower Yorktown Formation, about 4.5 to 4.3 million years ago), and madisonius during the Late Pliocene (Upper Yorktown Formation, about 4 to 3 million years ago). The species Chesapecten jeffersonius is the state fossil of Virginia. Its geographical distribution is limited to the Atlantic coastal plain of North America, from Florida to Delaware. The name Chesapecten derives from the Chesapeake Bay, where eroding cliffs and outcrops regularly expose specimens. The genus includes numerous species, such as C. coccymelus, C. jeffersonius, C. madisonius, C. marylandica, C. middlesexensis, and others.
Frequently Asked Questions
What is Chesapecten?
Chesapecten is an extinct genus of scallop placed in the family Pectinidae. It was the dominant scallop species in the shallow Mid-Atlantic marine environment during its tenure.
Where and when did Chesapecten live?
Its fossils appear in marine sediments along the Atlantic coastal plain, ranging from Florida up to Delaware. The genus spans from the early Miocene through the early Pleistocene epochs.
What does a Chesapecten shell look like?
The shell shows broad radial ribs fanning outward from the umbo, intersected by finer, rougher ribs that run parallel to the shell margins. The left valve is noticeably more curved than the right.
Why is Chesapecten considered important?
The species Chesapecten jeffersonius is designated as the official state fossil of Virginia. It also represents the most common scallop in Mid-Atlantic seas for millions of years, making it a key indicator of those ancient coastal ecosystems.
When was Chesapecten first recognized in science?
A shell was illustrated back in 1687 in Martin Lister's Historiae Conchyliorum, but the genus received its formal scientific name in 1975 from paleontologists Ward and Blackwater. Harold E. Vokes confirmed its placement in Pectinidae in 1980.
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