References
Reference
Druckenmiller, Pat S. (2006) Early Cretaceous plesiosaurs (Sauropterygia: Plesiosauria) from northern Alberta: palaeoenvironmental and systematic implications; PhD, pp.581
Early Cretaceous plesiosaurs (Sauropterygia: Plesiosauria) from northern Alberta: palaeoenvironmental and systematic implications
Principal Author
Pat S. Druckenmiller
Header
PhD Thesis
School
Department of Biological Sciences, University of Calgary
Editor
Anthony P. Russell, John-Paul Zonneveld, Derek A. Sikes, Edward D. Ghent
Volume
PhD
Pages
581
Abstract
Oil sands mining in northern Alberta by Syncrude Canada Ltd. has resulted in the
serendipitous discovery of seven plesiosaurs and two ichthyosaurs from the Lower
Cretaceous Clearwater Formation. Facies analysis has revealed that deposition of the
Wabiskaw Member, from which eight of the nine specimens were recovered, occurred in
the lower shoreface to offshore transition zone. The systematic and consistent manner in
which overburden is removed, coupled with the non-random distribution of the
specimens, both vertically and laterally within the succession, suggest a habitat
preference for this setting by marine vertebrates compared to deeper water environments.
Analysis of matrix blocks associated with the most complete and articulated plesiosaur,
TMP 94.122.01, indicates its rapid burial by storm sands.
The Syncrude fossils significantly increase our knowledge of Early Cretaceous
plesiosaur diversity. TMP 94.122.01 is a new taxon of short-necked plesiosaur, and is
one of the most complete and well-preserved specimens from North America. A second,
partially articulated skeleton is referred to Polycotylidae, as traditionally recognized.
Three of the specimens are referable to Elasmosauridae, of which two represent early and
late ontogenetic stages of a new taxon. Two of the plesiosaurs are fragmentary and
taxonomically indeterminate. Both ichthyosaurs are tentatively referred to
Platypterygius.
185 characters applicable to plesiosaur systematics are described and critically
reappraised. A phylogenetic analysis of 30 terminal units scored for 152 characters
indicates a basal division of plesiosaurs into two major clades of short-necked (traditional
pliosauroids) and long-necked (plesiosauroids) taxa. Among short-necked plesiosaurs, a
sister group relationship between TMP 94.122.01 and traditionally recognized
Polycotylidae (Dolichorhynchops + Edgarosaurus) is recovered. This clade, in turn, is
the sister taxon to Leptocleididae, consisting of Leptocleidus and an unnamed Australian
taxon, AM F99374. Together, these two clades constitute a newly recognized taxon of
Cretaceous short-necked plesiosaurs, Leptocleidoidea. Contrary to predictions, TMP
94.122.01 and Leptocleidus are not sister taxa.
serendipitous discovery of seven plesiosaurs and two ichthyosaurs from the Lower
Cretaceous Clearwater Formation. Facies analysis has revealed that deposition of the
Wabiskaw Member, from which eight of the nine specimens were recovered, occurred in
the lower shoreface to offshore transition zone. The systematic and consistent manner in
which overburden is removed, coupled with the non-random distribution of the
specimens, both vertically and laterally within the succession, suggest a habitat
preference for this setting by marine vertebrates compared to deeper water environments.
Analysis of matrix blocks associated with the most complete and articulated plesiosaur,
TMP 94.122.01, indicates its rapid burial by storm sands.
The Syncrude fossils significantly increase our knowledge of Early Cretaceous
plesiosaur diversity. TMP 94.122.01 is a new taxon of short-necked plesiosaur, and is
one of the most complete and well-preserved specimens from North America. A second,
partially articulated skeleton is referred to Polycotylidae, as traditionally recognized.
Three of the specimens are referable to Elasmosauridae, of which two represent early and
late ontogenetic stages of a new taxon. Two of the plesiosaurs are fragmentary and
taxonomically indeterminate. Both ichthyosaurs are tentatively referred to
Platypterygius.
185 characters applicable to plesiosaur systematics are described and critically
reappraised. A phylogenetic analysis of 30 terminal units scored for 152 characters
indicates a basal division of plesiosaurs into two major clades of short-necked (traditional
pliosauroids) and long-necked (plesiosauroids) taxa. Among short-necked plesiosaurs, a
sister group relationship between TMP 94.122.01 and traditionally recognized
Polycotylidae (Dolichorhynchops + Edgarosaurus) is recovered. This clade, in turn, is
the sister taxon to Leptocleididae, consisting of Leptocleidus and an unnamed Australian
taxon, AM F99374. Together, these two clades constitute a newly recognized taxon of
Cretaceous short-necked plesiosaurs, Leptocleidoidea. Contrary to predictions, TMP
94.122.01 and Leptocleidus are not sister taxa.
Language
English