Spencer Lucas
Spencer G. Lucas is a stratigrapher and paleontologist who has been Curator of Geology and Paleontology at the New Mexico Museum of Natural History and Science (Albuquerque, New Mexico, USA) since 1988. He received a B. A. degree from the University of New Mexico (1976) and M. S. (1979) and Ph.D. (1984) degrees from Yale University. Lucas’s research has focused on biostratigraphic problems of the late Paleozoic, Mesozoic and early Cenozoic. Since 1992, he has been a major contributor to refinement of the Triassic timescale as a Voting Member of the IUGS Subcommission on Triassic Stratigraphy. He has undertaken extensive field research in the American West, Kazakstan, China, Mexico, Nicaragua and Costa Rica.
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Permian boundary in Abo Canyon, New Mexico. Charles B. Read collected the fossils in 1940 and 1941; Read’s
field notes cannot be located. A combination of Read’s bed numbering pattern, his notes in the collections, and collection
taxonomic composition permits them to be placed in an oldest to youngest sequence. The youngest fossils, from the Abo
Formation of early Permian age, anchor the collection stratigraphically. A collection labeled “Base of Red Magdalena” is most
likely equivalent to the modern Bursum Formation, thus immediately below the Abo. The three remaining collections are from
the Upper Pennsylvanian portion of the Atrasado Formation. All collections are dominated or codominated by plants typical
of environments with seasonal moisture stress and record increasing moisture limitation through time. Conifers, Sphenopteris
germanica, and mixoneurid odontopterids are common to abundant in pre–Abo Formation collections. These same collections
also contain wet-substrate taxa, particularly calamitaleans and marattialean tree ferns, with arborescent lycopsids in the oldest
collection. The middle three collections contain the remains of microconchids/spirorbids, snails, ostracods, and conchostracans
closely associated with the plant remains, indicating brackish to marine salinities at the burial sites of the organics. The Abo
Pass collections document Pennsylvanian–Permian floristic changes in the western Pangean equatorial belt, an important point
of comparison to better studied floras from this same interval in central Pangea (eastern United States and Europe). Most of the
plants in the western equatorial assemblages are the same as those of similar age from west central to central Pangea (Euramerica),
indicating a widespread tropical biogeographic province at this time, but within which there were several distinct biomes.
Permian boundary in Abo Canyon, New Mexico. Charles B. Read collected the fossils in 1940 and 1941; Read’s
field notes cannot be located. A combination of Read’s bed numbering pattern, his notes in the collections, and collection
taxonomic composition permits them to be placed in an oldest to youngest sequence. The youngest fossils, from the Abo
Formation of early Permian age, anchor the collection stratigraphically. A collection labeled “Base of Red Magdalena” is most
likely equivalent to the modern Bursum Formation, thus immediately below the Abo. The three remaining collections are from
the Upper Pennsylvanian portion of the Atrasado Formation. All collections are dominated or codominated by plants typical
of environments with seasonal moisture stress and record increasing moisture limitation through time. Conifers, Sphenopteris
germanica, and mixoneurid odontopterids are common to abundant in pre–Abo Formation collections. These same collections
also contain wet-substrate taxa, particularly calamitaleans and marattialean tree ferns, with arborescent lycopsids in the oldest
collection. The middle three collections contain the remains of microconchids/spirorbids, snails, ostracods, and conchostracans
closely associated with the plant remains, indicating brackish to marine salinities at the burial sites of the organics. The Abo
Pass collections document Pennsylvanian–Permian floristic changes in the western Pangean equatorial belt, an important point
of comparison to better studied floras from this same interval in central Pangea (eastern United States and Europe). Most of the
plants in the western equatorial assemblages are the same as those of similar age from west central to central Pangea (Euramerica),
indicating a widespread tropical biogeographic province at this time, but within which there were several distinct biomes.
of the Mesozoic Era, lasted approximately 145 to 66 Ma (79 million
years) and witnessed important changes to life on Earth, from the
minor extinction event before the end of the Jurassic Period (145.5
Ma) to the Cretaceous-Paleogene (K-Pg) mass extinction dated at 66
Ma. Paleontological research on the Cretaceous Period has become
very significant during the last three decades because of the worldwide
discoveries of dinosaurs, foraminiferans, primitive mammals, marine
reptiles such as ichthyosaurs, plesiosaurs, and mosasaurs, sharks,
ammonites and flora such as angiosperms. The Cretaceous is well
known from India by marine sections in the Cauvery basin, south India
and freshwater terrestrial deposits in east-central and western India.
Cretaceous rocks also crop out in some regions in eastern China, Japan,
Korea, Philippines, Thailand, Cambodia, Laos, Vietnam, Madagascar,
Iran, Kazakhstan, Denmark, Australia, New Zealand, central and
southeastern South America, including Patagonia and Brazil, and
Mexico, etc. Cretaceous rocks in both Europe (France, Austria,
Hungary, northwestern Spain, Portugal, Germany, Iberia and Romania)
and North America reflect the great extent of epicontinental seas over
the Cretaceous continents
in Honduras. In 1859, American archaeologist Ephraim George Squier also mentioned these fossils, illustrating a lower jaw fragment with a molar and providing specific clues to the location of the bonebed. J. M. Dow subsequently gave a gomphothere molar from the locality to Joseph Leidy at the Academy of Natural Sciences in Philadelphia, USA. Leidy published on the fossil, which still remains in the collection of the Academy, as “Mastodon ohioticus” or as M. andium, and it was later referred to Rhynchotherium by Osborn and others. This molar is best identified as Cuvieronius
hyodon, and the bonebed from which it was derived is near the modern village of Humuya (Tambla in the 1800s), not near the village currently called Tambla. The Tambla “mastodon bed” has never been relocated, though data provided here should make that possible. Its discovery in the 1850s did not encourage further exploration for vertebrate fossils in Honduras, probably because “mastodon” fossils were already commonplace in the USA, so the Tambla bonebed did not constitute a remarkable discovery.
Keywords: Honduras, Tambla, Humuya, gomphothere, mastodon
RESUMEN: En 1858, el geólogo estadounidense Joseph LeConte publicó el primer reporte científico de una fósil vertebrado en América Central, registrado como una “capa de mastodonte” cerca del pueblo de Tambla en Honduras. En 1859, el arqueólogo estadounidense Ephraim George Squier también mencionó estos fósiles, ilustrando un fragmento de la mandíbula inferior con un molar y aportó las claves específicas de la localización de la capa de huesos. J.M. Dow subsecuentemente donó el molar de mastodonte a Joseph Leidy, de la Academia de Ciencias Naturales de Filadelfia, identificado como “Mastodon ohioticus” o como M. andium, y que fue más tarde referido como Rhynchotherium por Osborn y otros. Leidy publicó sobre el fósil, el cual todavía permanece en la colección de dicha academia. Así este molar es mejor identificado, al día de hoy, como un Cuvieronius hyodon, y la capa fosilífera del cual proviene se localiza cerca del rebautizado pueblo de Humuya (llamada Tambla en el siglo XIX), lejos del actual pueblo de Tambla. La “capa de mastodonte” de Tambla nunca ha sido relocalizada; por ello, los datos acá aportados deberían de hacerlo posible. Su descubrimiento en los mediados de la década de los cincuenta del siglo antepasado no motivó mayores exploraciones de fósiles de vertebrados en Honduras, quizás debido a que los mastodontes eran en ese entonces hallazgos frecuentes
en EE.UU, así que la capa fosilífera de Tambla no constituyó un descubrimiento sobresaliente.
Palabras clave: Honduras, Tambla, Humuya, gonfoterio, mastodonte