Ordovician Period (490 mya- 443 mya)
During the Ordovician period, there were two records of plant fossils. The first record was a plant megafossil, and the second was a record of dispersed spore fossils. The megafossil plant record has fossils of significant parts of the actual plant. The fossils of the earliest plants are highly biased and incomplete. These floras were largely diminutive and did not have recalcitrant tissues or had minimal resistant tissues (Wellman et al., 2013, p.2). Therefore, the earliest plants were unlikely to be preserved.
There were only 23 reported sites with the Ordovician terrestrial plants. The early plant fossil was very biased ad favored plants with recalcitrant tissues. Most of the early flora were ‘bryophyte-like’ in structure. Plant fossils in the Ordovician period were conserved in rare circumstances of exceptional conservation. During the Ordovician period, the fish’s eyes were bigger; however, they evolved and were reduced (Schoenemann, 2018, p.277). Besides, fish had a simple lens and compound eyes.
Carboniferous Period (354 mya- 290 mya)
During the Carboniferous Period, reptiles that relied on water bodies for egg-laying evolved from amphibians. These reptiles did not exploit arid environments far from water bodies. Also, the reptiles innovated giant yolk-laden bombed eggs that could be positioned on land to develop as embryos (Aretz et al., 2020, p..5).
Synapsids fragmented from the primitive reptile group in the early phases of evolution, possibly in the mid-Carboniferous period.
Synapsids had begun to develop characteristics of mammals that made them be active predators and fleet-footed. The legs of Synapsids started to move under the body. Besides, false palate and Heterodyne dentition began to develop in pelycosaurs and formed therapsids. There were two types of Synapsids during a carboniferous period, including advanced therapsids and primitive Pelycosaurs (Kimura, 2020, p.39). Sauropsids were dinosaurs with pelvic girdles similar to lizards. The pubis and ischium bones of Sauropsids radiated further from each other.
Permian Period (290 mya- 248 mya)
The Permian Period (290–245 million years ago) involved the largest mass extinction ever witnessed. All the main landmasses crashed to form a supercontinent referred to as Pangaea. There were extreme temperatures and dry climates (Henderson et al., 2020, p.896). Animals and plants which existed during Permian Period developed adaptations of dryness like leathery skin and waxy leaves to prevent water loss. Permian Period came to an end with mass extinction.
The supercontinent Pangaea incorporated continents of all of today’s land in one landmass. The mass extinction at the end of the Permian Period led to the extinction of most species, but some plants survived it (Gastaldo, 2019, p.4). Some of the possible reasons for the mass extinction are meteorites hitting the earth, and enormous volcanoes sweeping gases and ashes into the air. The two happenings could have darkened skies for many months with dust. The extinction experiences in Permian Period paved the start of the Triassic period.
Triassic Period
The regression of marine life manifested at the end of the Permian and the commencement of the Triassic period. They originated from the margins of the one supercontinent Pangaea. The period also had the most adverse mass destruction of the Phanerozoic (Scanlon, 2006, p.275). During the Triassic period, there were progressive dry and warm climates. Climate change resulted in the adaptive radiation of the g reptile lineages, which survived the mass extinction.
Groups like mosasaurs, pterosaurs, turtles, and early divisions of the amniotes radiation that did not endure the Triassic, have limited fossils present. However, some reptiles and dinosaurs survived extinction and produced a sharp increase in variety interrupted by further extinction waves (Benton et al., 2014, p.90). Minor groups survived until the end of the Triassic period. Contiguous terrestrial masses were barriers to the migration of reptiles during the Triassic period despite massive and large desert areas in lower latitudes.
References
Aretz, M., Herbig, H.G., Wang, X.D., Gradstein, F.M., Agterberg, F.P. and Ogg, J.G., 2020. The Carboniferous Period. In Geologic Time Scale 2020 (pp. 811-874). Elsevier.
Benton, M.J., Forth, J. and Langer, M.C., 2014. Models for the rise of the dinosaurs. Current Biology, 24(2), pp.R87-R95.
Gastaldo, R.A., 2019. Ancient plants escaped the end-Permian mass extinction.
Henderson, C.M., Shen, S.Z., Gradstein, F.M. and Agterberg, F.P., 2020. The Permian Period. In Geologic Time Scale 2020 (pp. 875-902). Elsevier.
Kimura, M., 2020. Tracing the Course of Evolution. In My Thoughts on Biological Evolution (pp. 35-48). Springer, Singapore.
Scanlon, J.D., 2006. Dinosaurs and other Mesozoic reptiles of Australasia. Evolution and biogeography of Australian vertebrates. Sydney: Australian Scientific Publishing, pp.265-290.
Schoenemann, B., 2018. Evolution of eye reduction and loss in trilobites and some related fossil arthropods. Emerging Science Journal, 2(5), pp. 272-286.
Wellman, C.H., Steemans, P. and Vecoli, M., 2013. Palaeophytogeography of Ordovician–Silurian land plants. Geological Society, London, Memoirs, 38(1), pp. 461-476.