BITTEN  TRILOBITES

 

Trilobites are important and common fossils in Paleozoic rocks, especially in the Cambrian.  Much is known about their paleobiology, ontogeny, evolutionary patterns, etc.  One of the less well known aspects of trilobitology is the significance of malformations, or deformities in the preserved exoskeleton.  One category of trilobite malformation is healed bite marks.  Below are photos of three different bitten trilobite specimens.

 


 

Elrathia kingii (Meek, 1870) trilobite with healed bite mark (2.8 cm long) from the Wheeler Formation (Middle Cambrian) of western Utah’s House Range.  This is one of the most abundantly preserved trilobites species on Earth.  It is affectionately called “Joe Trilobite” by some trilobite workers.  Elrathia kingii is abundantly preserved in the Wheeler Formation of the House Range in northern Millard County, western Utah, USA.  Many specimens are commercially prepared and sold throughout America.  Occasionally, specimens can be found with healed bite marks.  This Elrathia trilobite has a healed bite mark on the left pleural lobe of the posterior thorax.  Three pleurae are strongly malformed.  Most bites on trilobites are blamed on unsuccessful anomalocaridid predation, but other Cambrian organisms are also known to have preyed on trilobites.

Classification: Arthropoda, Trilobita, Polymerida, Alokistocaridae

Stratigraphy & age: upper Ptychagnostus atavus Interval-zone (= lower Bolaspidella Assemblage-zone), Wheeler Formation, upper Middle Cambrian

 


  

Isotelus maximus Locke, 1838 trilobite with healed bite mark (above & below) from the Arnheim Formation (Upper Ordovician) of southwestern Ohio’s Flat Run Trilobite Lagerstätte.  This large outstretched specimen has a healed injury on the right side of the cephalon (head).  The exoskeleton has partially regenerated and a small, anomalous genal spine has started growing.  The regenerated exoskeleton indicates that the injury was not lethal - the bite mark is evidence of unsuccessful predation.

This trilobite specimen, plus the large enrolled specimen shown below, have healed bite marks on their right sides.  Published census information of bitten trilobites has shown that a statistically significant percentage of specimens have bite marks on their right sides.  This is a great example of “handedness” (behavioral lateralization) in the fossil record.

Classification: Arthropoda, Trilobita, Polymerida, Asaphidae

Stratigraphy & age: Flat Run Trilobite Lagerstätte, near-top Sunset Member, mid-Arnheim Formation, lower Richmondian Stage, upper Cincinnatian Series, upper Upper Ordovician

Locality: Flat Run Trilobite Quarry, far-southern Clay Township, far-southwestern Highland County, just E of Sicily, E of Mt. Orab, southwestern Ohio, USA.

Collected & prepared by Dan Cooper.

Public display at Ohio State University’s Orton Geology Museum (Columbus, Ohio, USA).

 


 

Isotelus maximus Locke, 1838 trilobite with healed bite mark (above & below) from the Arnheim Formation (Upper Ordovician) of southwestern Ohio’s Flat Run Trilobite Lagerstätte.  This large enrolled specimen has a bite mark on the right side of the pygidium (tail).  Notice the scalloped edges of the bite mark - this reflects the morphology of the attacker’s mouth parts.

Classification: Arthropoda, Trilobita, Polymerida, Asaphidae

Stratigraphy & age: Flat Run Trilobite Lagerstätte, near-top Sunset Member, mid-Arnheim Formation, lower Richmondian Stage, upper Cincinnatian Series, upper Upper Ordovician

Locality: Flat Run Trilobite Quarry, far-southern Clay Township, far-southwestern Highland County, just E of Sicily, E of Mt. Orab, southwestern Ohio, USA.

Collected & prepared by Dan Cooper.

Public display at Ohio State University’s Orton Geology Museum (Columbus, Ohio, USA).

  


 

For more info. on bitten and malformed trilobites and behavioral asymmetry, see the following papers (& the papers cited in them):

 

Babcock & Robison (1989) - Nature 337: 695-696.

 

Babcock (1993) - Journal of Paleontology 67: 217-229.

 

Babcock (2007) - Role of malformations in elucidating trilobite paleobiology: a historical synthesis.  in  Fabulous fossils - 300 years of worldwide research on trilobites.  New York State Museum Bulletin 507: 3-19.

 


 

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