The shorebird-duck mosaic bird, Presbyornis, is best known from the Eocene Green River Formation where it often occurs in local monospecific bonebeds, suggestive of mass mortality events. The sedimentology, paleontology, taphonomy, XRD mineralogy, and the carbonate stable isotope signature (δ18O) of one of these bonebeds was studied on the southern margin of Eocene Fossil Lake.
A series of 408 standardized radiographs were used to construct the first large scale radiograph aided taphonomic map of a vertebrate fossil quarry (3,874 bones were recorded in 11.5 m2). A small group of 100 bones (including a complete skull and sternum) were removed from the micrite matrix to provide the first nearly complete composite skeleton of Middle Eocene Presbyornis. This is the first reported taphonomic map of an avian fossil quarry, the strongest evidence of associated Presbyornis skeletons, and the strongest linkage of mass avian death with Clostridium botulinum neurotoxin in the paleontologic literature.
At this Presbyornis site, two distinct mass mortality events are evident. The first event (lowest in the section) is a widespread aquatic gastropod mortality with localized eggshell and a few Presbyornis bones. This gastropod mortality event occurred on a surface of nondeposition. The second event (2 cm higher) is a broad strandline deposit of at least 66 Presbyornis carcasses (MNI=66).
This surface of nondeposition may represent a time when the gastropods colonized the lake bottom. This colonization was likely followed by a rapid lake regression, which exposed the carbonate mudflat, killed aquatic invertebrates, and enhanced the incubation of C. botulinwn within the decaying invertebrates. The exposed mudflat accumulated eggshell fragments and a few bones, as neurotoxins killed a large number of Presbyornis. Disarticulation of the avian carcasses preceded another freshwater transgression of the lake which deposited the avian bones along strandlines and preserved them within the next unit of rapidly deposited ostracodal calcimicrite.
Analogous modem avian botulism epizootics are often preceded by a mass mortality of aquatic invertebrates, which are exposed and killed by rapid shoreline regression. Many mechanisms have been proposed for mass mortality of waterfowl. The evidence from this site is most consistent with an interpretation of mass avian death due to ingestion of C. botulinwn neurotoxin.
","abstract_html":"<p>The shorebird-duck mosaic bird, <em>Presbyornis</em>, is best known from the Eocene Green River Formation where it often occurs in local monospecific bonebeds, suggestive of mass mortality events. The sedimentology, paleontology, taphonomy, XRD mineralogy, and the carbonate stable isotope signature (δ<sup>18</sup>O) of one of these bonebeds was studied on the southern margin of Eocene Fossil Lake.</p> <p>A series of 408 standardized radiographs were used to construct the first large scale radiograph aided taphonomic map of a vertebrate fossil quarry (3,874 bones were recorded in 11.5 m<sup>2</sup>). A small group of 100 bones (including a complete skull and sternum) were removed from the micrite matrix to provide the first nearly complete composite skeleton of Middle Eocene <em>Presbyornis</em>. This is the first reported taphonomic map of an avian fossil quarry, the strongest evidence of associated <em>Presbyornis</em> skeletons, and the strongest linkage of mass avian death with <em>Clostridium botulinum</em> neurotoxin in the paleontologic literature.</p> <p>At this <em>Presbyornis </em>site, two distinct mass mortality events are evident. The first event (lowest in the section) is a widespread aquatic gastropod mortality with localized eggshell and a few <em>Presbyornis</em> bones. This gastropod mortality event occurred on a surface of nondeposition. The second event (2 cm higher) is a broad strandline deposit of at least 66 <em>Presbyornis</em> carcasses (MNI=66).</p> <p>This surface of nondeposition may represent a time when the gastropods colonized the lake bottom. This colonization was likely followed by a rapid lake regression, which exposed the carbonate mudflat, killed aquatic invertebrates, and enhanced the incubation of <em>C. botulinwn</em> within the decaying invertebrates. The exposed mudflat accumulated eggshell fragments and a few bones, as neurotoxins killed a large number of <em>Presbyornis</em>. Disarticulation of the avian carcasses preceded another freshwater transgression of the lake which deposited the avian bones along strandlines and preserved them within the next unit of rapidly deposited ostracodal calcimicrite.</p> <p>Analogous modem avian botulism epizootics are often preceded by a mass mortality of aquatic invertebrates, which are exposed and killed by rapid shoreline regression. Many mechanisms have been proposed for mass mortality of waterfowl. The evidence from this site is most consistent with an interpretation of mass avian death due to ingestion of <em>C. botulinwn</em> neurotoxin.</p>","abstract_has_math":false,"creators":["Leggitt, V. Leroy"],"institution":null,"degree_name":"Master of Science (MS)","degree_level":"Thesis","degree_discipline":"Paleontology","degree_department":null,"school":null,"contributors":["H. Paul Buchheim","Leonard R. Brand","Robert A. Cushman, Jr."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":1996,"date_issued":"1996-06-01T07:00:00Z","date_published":"1996-06-01T07:00:00Z","updated_at":"2026-07-24T02:54:01Z","subjects":["Earth Sciences","Ornithology","Paleontology","Sedimentology","Avian botulism -- Wyoming -- Lincoln County; Birds Fossil -- Wyoming -- Lincoln County; Presbyornis"],"languages":["English"],"rights":["This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights."],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarsrepository.llu.edu/etd/1491","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["H. Paul Buchheim","Leonard R. Brand","Robert A. Cushman, Jr."]},{"key":"dc:creator","label":"Author","values":["Leggitt, V. Leroy"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"thesis:degree_discipline","label":"Discipline","values":["Paleontology"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science (MS)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Earth Sciences","Ornithology","Paleontology","Sedimentology","Avian botulism -- Wyoming -- Lincoln County; Birds Fossil -- Wyoming -- Lincoln County; Presbyornis"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["English"]},{"key":"dc:rights","label":"Dc Rights","values":["This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarsrepository.llu.edu/etd/1491"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The shorebird-duck mosaic bird, Presbyornis, is best known from the Eocene Green River Formation where it often occurs in local monospecific bonebeds, suggestive of mass mortality events. The sedimentology, paleontology, taphonomy, XRD mineralogy, and the carbonate stable isotope signature (δ18O) of one of these bonebeds was studied on the southern margin of Eocene Fossil Lake.
A series of 408 standardized radiographs were used to construct the first large scale radiograph aided taphonomic map of a vertebrate fossil quarry (3,874 bones were recorded in 11.5 m2). A small group of 100 bones (including a complete skull and sternum) were removed from the micrite matrix to provide the first nearly complete composite skeleton of Middle Eocene Presbyornis. This is the first reported taphonomic map of an avian fossil quarry, the strongest evidence of associated Presbyornis skeletons, and the strongest linkage of mass avian death with Clostridium botulinum neurotoxin in the paleontologic literature.
At this Presbyornis site, two distinct mass mortality events are evident. The first event (lowest in the section) is a widespread aquatic gastropod mortality with localized eggshell and a few Presbyornis bones. This gastropod mortality event occurred on a surface of nondeposition. The second event (2 cm higher) is a broad strandline deposit of at least 66 Presbyornis carcasses (MNI=66).
This surface of nondeposition may represent a time when the gastropods colonized the lake bottom. This colonization was likely followed by a rapid lake regression, which exposed the carbonate mudflat, killed aquatic invertebrates, and enhanced the incubation of C. botulinwn within the decaying invertebrates. The exposed mudflat accumulated eggshell fragments and a few bones, as neurotoxins killed a large number of Presbyornis. Disarticulation of the avian carcasses preceded another freshwater transgression of the lake which deposited the avian bones along strandlines and preserved them within the next unit of rapidly deposited ostracodal calcimicrite.
Analogous modem avian botulism epizootics are often preceded by a mass mortality of aquatic invertebrates, which are exposed and killed by rapid shoreline regression. Many mechanisms have been proposed for mass mortality of waterfowl. The evidence from this site is most consistent with an interpretation of mass avian death due to ingestion of C. botulinwn neurotoxin.
"]},{"key":"dc:title","label":"Title","values":["An Avian Botulism Epizootic Affecting a Nesting Site Population of Presbyornis : on a Carbonate Mudflat Shoreline of Eocene Fossil Lake"]}]}],"canonical_facts":{"dc:contributor":["H. Paul Buchheim","Leonard R. Brand","Robert A. Cushman, Jr."],"dc:creator":["Leggitt, V. Leroy"],"dc:description.abstract":["The shorebird-duck mosaic bird, Presbyornis, is best known from the Eocene Green River Formation where it often occurs in local monospecific bonebeds, suggestive of mass mortality events. The sedimentology, paleontology, taphonomy, XRD mineralogy, and the carbonate stable isotope signature (δ18O) of one of these bonebeds was studied on the southern margin of Eocene Fossil Lake.
A series of 408 standardized radiographs were used to construct the first large scale radiograph aided taphonomic map of a vertebrate fossil quarry (3,874 bones were recorded in 11.5 m2). A small group of 100 bones (including a complete skull and sternum) were removed from the micrite matrix to provide the first nearly complete composite skeleton of Middle Eocene Presbyornis. This is the first reported taphonomic map of an avian fossil quarry, the strongest evidence of associated Presbyornis skeletons, and the strongest linkage of mass avian death with Clostridium botulinum neurotoxin in the paleontologic literature.
At this Presbyornis site, two distinct mass mortality events are evident. The first event (lowest in the section) is a widespread aquatic gastropod mortality with localized eggshell and a few Presbyornis bones. This gastropod mortality event occurred on a surface of nondeposition. The second event (2 cm higher) is a broad strandline deposit of at least 66 Presbyornis carcasses (MNI=66).
This surface of nondeposition may represent a time when the gastropods colonized the lake bottom. This colonization was likely followed by a rapid lake regression, which exposed the carbonate mudflat, killed aquatic invertebrates, and enhanced the incubation of C. botulinwn within the decaying invertebrates. The exposed mudflat accumulated eggshell fragments and a few bones, as neurotoxins killed a large number of Presbyornis. Disarticulation of the avian carcasses preceded another freshwater transgression of the lake which deposited the avian bones along strandlines and preserved them within the next unit of rapidly deposited ostracodal calcimicrite.
Analogous modem avian botulism epizootics are often preceded by a mass mortality of aquatic invertebrates, which are exposed and killed by rapid shoreline regression. Many mechanisms have been proposed for mass mortality of waterfowl. The evidence from this site is most consistent with an interpretation of mass avian death due to ingestion of C. botulinwn neurotoxin.
"],"dc:identifier":["https://scholarsrepository.llu.edu/etd/1491"],"dc:language":["English"],"dc:rights":["This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights."],"dc:subject":["Earth Sciences","Ornithology","Paleontology","Sedimentology","Avian botulism -- Wyoming -- Lincoln County; Birds Fossil -- Wyoming -- Lincoln County; Presbyornis"],"dc:title":["An Avian Botulism Epizootic Affecting a Nesting Site Population of Presbyornis : on a Carbonate Mudflat Shoreline of Eocene Fossil Lake"],"thesis:degree_discipline":["Paleontology"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["Master of Science (MS)"]},"updated_at":"2026-07-24T02:54:01Z"}