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Pennsylvanian Age Fossils of Northeastern Illinois, USA 1Fossil Shark Egg Cases of the Mazon Creek Region
The Field MuseumProduced by: Jack Wittry, Collection Associate, with assistance of Rosalba Rodriguez, Science and Education Dept.,The Field Museum. Photos © Jack Wittry; [[email protected]] © The Field Museum, Chicago, IL 60605 USA.Scale bar equals 1 cm. [fieldguides.fieldmuseum.org] [978] 2/2018
Around 307 mya northeasternIllinois was a tropical swampat the edge of a brackish sea.And was a nursery for thelargest and most diverse oc-currence of fossil shark eggcapsules in the world.
Fayolia ellipticus: The bandsare equal in width, and spiralat a low angle. The body lacksa beak and pedicle. Very rare.
Palaeoxyris prendeli
Palaeoxyris prendeli
Palaeoxyris prendeli: Generallyit has no visible bands, whenvisible they are very weak witha repeating pattern of small-broad-medium/broad-broad,which crosses the body mid-sec-tion at a 45° angle. A distortedarea is often seen just below themiddle of the body. Suture linesare often only visible on the
tendril orspine
beak
band
body
suture orcollaretteif it formsa wing
pedicle
pedicle tip. The pedicles arelong and narrow. Lesquereuxdescribed P. prendeli as oftenappearing like a “empty wrin-kled bag.” Easily this species isthe most common fossil sharkegg case found in North Amer-ica. And by far the most fre-quently found egg case in theMazon Creek biota.
Identification is based mostlyon band count, and band pat-tern. Also the relative dimen-sions of the various partsshould be considered if possi-ble. Overall size is not a diag-nostic feature. Larger sharkslaid large eggs. The differencecan be two to three timeslarger than a small example.
After Fisher, J. andWittry, J., 2014
Vetacapsula johnsoni: Spindle-shaped, with a large number ofvery fine, closely placed, paral-lel ribs, which run the length ofthe capsule. A median ridge isalso present. Very rare.
Vetacapsula cooperi: Bulb-shaped, with a large number ofstraight longitudinal ribs whichrun the length of the capsule. Amedian ridge is present. Veryrare.
Palaeoxyris helicteroides: Theband count is 8. Bands are wellmarked and form a repeatingpattern of small-broad, whichcrosses the body mid-section ata 45° angle. Rare.
Palaeoxyris carbonaria: Bandcount is 10 or more, and areequal in width. They cross thebody mid-section at a 30° angleand form a fine mesh. The beakis elongated and nearly equalin length to body. Collarettesare visible in well preservedspecimens. Rare.
Palaeoxyris warei: The bandcount is 4. They are of equalwidth, recessed in furrows, andcross body mid-section at a 30°angle. The sutures are promi-
Pennsylvanian Age Fossils of Northeastern Illinois, USA 2Fossil Shark Egg Cases of the Mazon Creek Region
The Field MuseumProduced by: Jack Wittry, Collection Associate, with assistance of Rosalba Rodriguez, Science and Education Dept.,The Field Museum. Photos © Jack Wittry; [[email protected]] © The Field Museum, Chicago, IL 60605 USA.Scale bar equals 1 cm. [fieldguides.fieldmuseum.org] [978] 2/2018
nent and are frequently seenslightly separated. The secondmost commonly found egg caseat Mazon Creek.
Palaeoxyris lewisi: The numberof bands is 10. They are in a re-peating pattern of broad-broad-small. Bands cross the bodymid-section at a 30° angle. Thethird most commonly found eggcase at Mazon Creek.
Palaeoxyris multiplicatum: Un-like other species of egg cases,the outer egg cover is rigid.When compressed it shattersinto broken elongated frag-ments. There are no known
complete examples of the bandpattern. Other than the shat-tered apparence it has two fea-tures that help separate it fromthe other egg cases. The su-tures abruptly change angle as
they enter the body from thebeak. And they are nearlystraight as they run down thepedicle. Rare.
Pennsylvanian Age Fossils of Northeastern Illinois, USA 3Fossil Shark Egg Cases of the Mazon Creek Region
The Field MuseumProduced by: Jack Wittry, Collection Associate, with assistance of Rosalba Rodriguez, Science and Education Dept.,The Field Museum. Photos © Jack Wittry; [[email protected]] © The Field Museum, Chicago, IL 60605 USA.Scale bar equals 1 cm. [fieldguides.fieldmuseum.org] [978] 2/2018