Halloween special IX: The Hounds of Tindalos and the Ediacaran fauna.

The Hounds of Tindalos, original Arkham House hardcover, 1946.

“Human beings as we know them are merely fractions, infinitesimally small fractions of one enormous whole. Every human being is linked with all the life that has preceded him on this planet. All of his ancestors are parts of him. Only time separates him from his forebears, and time is an illusion and does not exist.” The quote belongs to “The Hounds of Tindalos”, a short story, first published in the March 1929 issue of Weird Tales. The autor was American writer Frank Belknap Long (1901- 1994).  He was one of H. P. Lovecraft’s close friends and contributor to the Cthulhu Mythos.

“The Hounds of Tindalos” (also mentioned by Lovecraft in his short story “The Whisperer in Darkness”, 1931) are strange creatures that exist in the angles of time (while human beings descended from the curves of time) in the extremely distant past. They can travel through time and space impelled by hunger or other evil purpose. Although they are represented as hounds, their appearance is a mass of incomprehensible shapes. Geometry is a powerful presence in the story of Frank Belknap Long. Halpin Chalmers, one of the main characters, reveres Einstein as “a priest of transcendental mathematics”, and the hounds could be a representation of fractal forms of life.

Rangeomorph taxa illustrating the characteristic fractal-like branching and diversity of overall form. (a) Charnia masoni, (b) Rangea schneiderhoehni, (c) Hapsidophyllas flexibilis, (d) Fractofusus misrae, (e) Bradgatia sp. Scale bar: (a, e) 2 cm; (b) 1.5 cm; (c) 4 cm; and (d) 3 cm. From Butterfield, 2020

The diversity of shapes in the Ediacara biota (575–542 Ma) include some of the most enigmatic creatures in the fossil record. From discs to fronds, to segmented morphologies at least vaguely comparable with modern animals, alongside bizarre fractal constructions unknown in our modern world. Among them, rangeomorphs, with their fractal body plan, were the first substantially macroscopic organisms.

Rangeomorphs have been traditionally interpreted as sessile organisms that lived in deep- and shallow-marine depositional environments, and were ecologically analogous to sponges or anthozoan cnidarian. They are characterized by a broadly frond-like habit. The arrangement of their branches has been proposed as a basis for distinguishing between taxa. The group dominated the Ediacaran ecosystems and provided key insights into the early evolution of multicellular eukaryotes. But at the the beginning of the Cambrian period, the ecological and geochemical conditions where the rangeomorphs were optimized changed, and their extraordinary body plan was lost forever.

References:

Long, Frank Belknap. “The Hounds of Tindalos” (1929). In Tales of the Cthulhu Mythos (1st ed.)

G.M. Narbonne, The Ediacara Biota: Neoproterozoic origin of animals and their ecosystems, Annual Review of Earth and Planetary Sciences, 33 (2005), pp. 421-442 (1)

D.H. Erwin, M. Laflamme, S.M. Tweedt, E.A. Sperling, D. Pisani, K.J. Peterson, The Cambrian conundrum: early divergence and later ecological success in the early history of animals
Science, 334 (2011), DOI: 10.1126/science.1206375

N.J. Butterfield. Constructional and functional anatomy of Ediacaran rangeomorphs. Geological Magazine (2020) https://doi.org/10.1017/S0016756820000734

 

Mussaurus and the social behaviour of early sauropodomorphs

Mussaurus patagonicus with neonate individuals. Credit: Jorge Gonzalez.

Sauropods were the largest terrestrial vertebrates. Their morphology is easy recognizable: a long, slender neck and a tail at the end of a large body supported by four columnar limbs. They were the first successful group of herbivorous dinosaurs, dominating most terrestrial ecosystems from the Late Triassic to Late Cretaceous. The group evolved from small, gracile, bipedal forms, and the acquisition of giant body size occurred during the Jurassic. The early sauropodomorph Mussaurus patagonicus was originally described from several well-preserved post-hatchling specimens associated with egg remains found at Laguna Colorada Formation (Late Triassic/Early Jurassic) in Argentina. The remains were briefly described by Jose Bonaparte in 1979. Now, the discovery of 80 individuals of Mussaurus patagonicus, ranging from embryos to fully-grown adults, and more than 100 eggs, provides the earliest evidence of complex social behaviour.

Nest with eggs of Mussaurus patagonicus. Image credit: Diego Pol.

The new findings comprise skeletons of six different ontogenetic stages ranging from embryos to adult individuals, that are either fully-articulated or partially disassociated. Their bones show a 0.5 cm-wide phosphatic halo related to the microbial decomposition of soft-tissue, which suggests that the skeletons were buried relatively rapidly at the same time. Histological analysis of the juvenile aggregation suggests a fast growth rate, while the absence of lines of arrested growth (LAGs) in their femora, tibia, humeri, and ribs, combined with their size, indicate that they were possibly members of a single brood. The eggs and nests of Mussaurus were found in three distinct horizons in the middle of the Laguna Colorada Formation. X-ray computed tomography reveals that the eggs were arranged in two or three layers within elongate depressions or trenches that appear to have been purposely excavated.

The research team lead by Diego Pol calculated the site’s age at 193 million years, predating previous records of social behavior in dinosaurs by at least 40 My. The researchers also suggest that sociality may have influenced the early success and the first global radiation of sauropods.

 

References:

Pol, D., Mancuso, A.C., Smith, R.M.H. et al. Earliest evidence of herd-living and age segregation amongst dinosaurs. Sci Rep 11, 20023 (2021). https://doi.org/10.1038/s41598-021-99176-1

Bonaparte, J. F. & Vince, M. E. hallazgo del primer nido de dinosaurios triásicos (Saurischia, Prosauropoda), Triásico Superior de Patagonia, Argentina. Ameghiniana 16, 173–182 (1979).