Biology:Namornis
Namornis is an extinct oogenus of Struthioniformes that lived during the early to middle Miocene epoch of Namibia. There are currently two species that have been described belonging to this genus, N. elimensis and N. oshanai (the type species.)[1][2]
Material from this genus is younger than that of Tsondabornis but still among the oldest of the order.[2]
Etymology
Pickford states that species the name for N. elimensis refers to the Elim Gullies north of Sossus Vlei, eroded into the Tsondab Sandstone, where the type series was collected.[1]
Evolution
Pickford considered the early Miocene Tsondabornis eggshell as the direct predecessor of Namornis elimensis.[1]
Mikhailov and Zelenkov dispute this theory and instead consider it more likely that N. elimensis is not a descendant of Tsondabornis, but rather its own lineage of Struthionidae, which might have replaced Tsondabornis in Namibia towards the middle Miocene.[2]
Description
Namornis elimensis
The eggshells of Namornis elimensis range from 2.5 to 3.7 mm thick with the average being 3.2 mm thick. The external surface of Namornis elimensis is patterned in a complex undulating system of depressions and pore complexes. Material found at Tsondab Vlei have about 40 pore complexes per 4 cm² while material found at Elim and Diep Rivier have been reported to have 24-37 pore complexes per 4 cm². Its pores are arranged both in clusters in the depths of vermiform depressions and in sub-parallel slits similar to those seen in aepyornithoids. The edges of these slits are swollen.[1]
The holotype for this species consists of fragmentary remains of eggshells that were uncovered in Elim Gullies and Tsondab Sandstone dated to around 17-16.5 million years old. Strangely, remains of Namornis elimensis occur by themselves and at most occur in pairs. This results in their remains being found in small patches of shell fragments and not in immense concentrations of broken eggshells.[1]
Namornis oshanai
The eggshells of N. oshanai range in thickness 3.2 to 4 mm, with a mean thickness of 3.6 mm. This makes it notably thicker than those of extant ostriches and even several larger extinct species of related birds such as Pachystruthio pannonicus.[3] Sauer estimated that the egg of the previously mentioned Pachystruthio pannonicus has twice the volume of Struthio camelus and is comparable in size with the eggs of Namornis oshanai.[2]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Martin Pickford (2014). "New ratite eggshells from the Miocene of Namibia". Communications of the Geological Survey of Namibia 15: 70–90. https://www.mme.gov.na/files/publications/fc5_Pickford_New%20Ratite%20Eggshells.pdf.
- ↑ 2.0 2.1 2.2 2.3 Mikhailov, Konstantin E.; Zelenkov, Nikita (September 2020). "The late Cenozoic history of the ostriches (Aves: Struthionidae), as revealed by fossil eggshell and bone remains" (in en). Earth-Science Reviews. doi:10.1016/j.earscirev.2020.103270. https://linkinghub.elsevier.com/retrieve/pii/S0012825220303160.
- ↑ Sánchez-Marco, Antonio; Amiot, Romain; Angst, Delphine; Bailon, Salvador; Betancort, Juan Francisco; Buffetaut, Eric; García-Castellano, Emma; Guillén-Vargas, Lourdes et al. (2025-08-27). "Unraveling the Strange Case of the First Canarian Land Fauna (Lower Pliocene)" (in en). Fossil Studies 3 (3): Supplementary table 1. doi:10.3390/fossils3030013. ISSN 2813-6284.
 |  |
