Fig. 1:A superb specimen of Glanochthon angusta in matrix. This creature is roughly 80-100 cm in length. This genus is an example of a temnospondyl amphibian, a long-lived order of tetrapods that roamed aquatic and terrestrial enveionments from the Carboniferous to the Triassic. This piece is in the collections of the Royal Ontario Museum (Toronto, Canada). It was on display for some time in the foyer of the museum, prior to the COVID-19 pandemic, until it was rotated off the foyer in early September 2021, after the museum had reopened the public galleries. However, fossils at the museum were about to get an extra, high-profile exhibit (see Museum Moment, below).
"Rock of the Month # 247, posted for January 2022" ---
Glanochthon fossils up to 1 metre long were found in the Lower Permian Saar-Nahe basin of southwest Germany (Schoch and Witzman, 2009). Two species are distinguished, found in different geological and paleoecological settings. This specimen, of the species Glanochthon angusta, is found in the Humberg black shale unit.
Near-contemporaries in North America would have included Eryops, a giant primitive amphibian from the Permian of Texas (Alcosser et al., 1991). Seymouria (see, e.g., Fischer and Gayrard-Valy, 1978), originally found near Seymour, Texas, is another early form, which tend to have features common to reptiles as much as amphibians. Yet-older amphibian remains are preserved in the Lower Carboniferous strata of the Midland Valley of Scotland, between Edinburgh and Glasgow, in a fossil assemblage of terrestrial amphibians, arthropods and plants, which lived in and around shallow lakes associated with hot springs, which were favourable for the deposition of freshwater limestones with cherts (Milner, 1985).
Much more recently, many amphibians (along with the ancestors of modern reptiles,
mammals and birds) survived the Cretaceous-Tertiary (KT or K-Pg) extinction event
(Bossuyt and Milinkovitch, 2001). Approaching the cataclysm, interflow sediments in the Deccan volcanic
province of west-central India preserved
the assembled remains of fossil fish, amphibians, turtles, lizards, snakes, crocodiles, mammals and dinosaurs in floodplain lake sediments (Khajuria and Prasad, 1998).
The global fossil record indicates that dinosaurs declined in the late Maastrichtian and were, with pterosaurs, the only major terrestrial vertebrate group that became extinct at or near the KT boundary (Milner, 1998).
In the Tertiary era, the amber mines in the Dominican Republic display a notable occurrence and preservation of unusual fossils, including amphibian fossils and bird feathers
Bones and skulls make fine fossils, but amphibians, like dinosaurs,
have also yielded trails of their footprints. These tracks are
an example of so-called trace fossils (ichnofossils: Sarjeant, 1994)
which can give powerful clues to the mode of life of the
animals which created them so long ago.
MUSEUM MOMENT #8
Royal Ontario Museum, Toronto, December 2021
A large new exhibit, the "Willner Madge Collection. Dawn of Life", opened on the 2nd floor of the museum on Saturday 04 December 2021. This is the first new permanent gallery to open at the museum in decades, and was itself 10 years in development. The gallery features almost 1,000 specimens, 60% of them from fossil localities across Canada. The specimens vary in age from the distant Precambrian (Archean, circa 3700 Ma) to Triassic. One special exhibit displays 120 million years of evolution, showcased by finds from Ordovician, Silurian and Devonian strata in Ontario (480-360 Ma). These Paleozoic strata provide evidence for the increasing complexity and diversity of life forms: early marine creatures; the colonization of the land surface; and the rise of vertebrate genera, including the ancestors of modern amphibian, reptile and mammal lineages.
UPDATE TO BE ADDED SHORTLY
Alcosser,M, Eldredge,N and Gould,SJ (1991) Fossils: the Evolution and Extinction of Species. Princeton University Press, xx+220pp.
Bossuyt,F and Milinkovitch,MC (2001) Amphibians as indicators of early Tertiary "out of India" dispersal of vertebrates. Science 292, 93-95, 06 April.
Fischer,J-C and Gayrard-Valy,Y (1978) Fossils of All Ages. Grosset & Dunlap, New York, English translation of 1976 original in Fr.
Khajuria,CK and Prasad,GVR (1998) Taphonomy of a late Cretaceous mammal-bearing microvertebrate assemblage from the Deccan inter-trappean beds of Naskal, peninsular India. Palaeogeography, Paleoclimatology, Paleoecology 137, 153-172.
Milner,AR (1985) Scottish window on terrestrial life in the Lower Carboniferous. Nature 314, 320-321, 28 March.
Milner,AC (1998) Timing and causes of vertebrate extinction across the Cretaceous- Tertiary boundary. In `Meteorites: Flux with Time and Impact Effects' (Grady,MM, Hutchison,R, McCall,GJH and Rothery,DA, editors), Geol.Soc. Spec.Publ. 140, 278pp., 247-257.
Poinar,GA (1988) The amber ark. Natural History 97 no.12, 42-47, December.
Sarjeant,WAS (1994) Footprints in the sands of time: vertebrate footprints and the interpretation of past environments. Geoscience Canada 21, 77-87.
Schoch,RR and Witzmann,F (2009) The temnospondyl Glanochthon from the Permian Meisenheim Formation of Germany. Special Papers in Palaeontology 81. 121–136.
Visit the "Rock of the Month" Archives,
or browse by category in the
"Rock of the Month Index"