File:Catellocaula vallata in bryozoan (Kope Formation, Upper Ordovician; Carrollton, Kentucky, USA) 1.jpg

English: Catellocaula vallata Palmer & Wilson, 1988 - bioimmuration structures in a bryozoan colony from the Ordovician of Kentucky, USA.

This fossil is from the famous Cincinnatian Series of the tristate area of Ohio-Kentucky-Indiana. Rocks in the Cincinnatian were deposited in relatively shallow marine facies during the Late Ordovician. The Cincinnatian succession is mostly interbedded limestones and shales. Most of the limestones are event beds (= tempestites), deposited during ancient storms.

This is a trepostome bryozoan colony. Bryozoans are sessile, benthic, filter-feeding, colonial lophophorates. Most of them make calcareous skeletons. The irregularly-shaped pits are not part of the bryozoan's normal skeletal structure. They are not borings (drillholes), but pseudoborings. Specifically, these depressions and grooves are bioimmuration structures - the bryozoan slowly grew over one or more soft-bodied encrusters attached to its surface. This particular type of bioimmuration structure is Catellocaula vallata, a trace fossil formed by a bryozoan growing around an encrusting colonial tunicate (Animalia, Chordata, Urochordata / Tunicata) (= "sea squirts"). Well-formed Catellocaula specimens have scalloped to stellate-shaped pits.

Stratigraphy: float from the Southgate Member, Kope Formation, middle Edenian Stage, lower Cincinnatian Series, Upper Ordovician

Locality: slope exposures behind old gasoline station at Carrollton exit off Interstate 71, just southwest of Carrollton & just northwest of Langstaff, central Carroll County, northern Kentucky, USA (38° 38’ 48.10" North latitude, 85° 07’ 01.37" West longitude)

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See info. at: strata.uga.edu/cincy/fauna/tracefossils/Catellocaula.html and

en.wikipedia.org/wiki/Bioclaustration