genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
, the
Cambridge Greensand
The Cambridge Greensand is a geological unit in England whose strata are earliest Cenomanian in age. It lies above the erosive contact between the Gault Formation and the Chalk Group in the vicinity of Cambridgeshire, and technically forms the lo ...
of
England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
and the
Voronezh Region
Voronezh Oblast (russian: Воронежская область, Voronezhskaya oblast) is a federal subject of Russia (an oblast). Its administrative center is the city of Voronezh. Its population was 2,308,792 as of the 2021 Census.
Geography
V ...
of
Russia
Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eig ...
.
Description
''Maiaspondylus'' is known from the
holotype
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of sever ...
UALVP 45635, a disarticulated but nearly complete skeleton preserved in three dimensions and from the referred materials UALVP 45639, two articulated, partially preserved embryos and eight articulated
vertebra
The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...
e of an adult, UALVP 45640, 14 articulated vertebrae of a juvenile, UALVP 45640, 12 articulated vertebrae, UALVP 45642, a partial snout and left dentaries with teeth and UALVP 45643, a fragmentary snout. All specimens were collected at Hay River from the Loon River Formation, dating to the early
Albian
The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous Epoch/ Series. Its approximate time range is 113.0 ± 1.0 Ma to 100.5 ± 0 ...
million years ago
The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds.
Usage
Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago) ...
.
All ''Maiaspondylus'' specimens were originally referred to ''
Platypterygius
''Platypterygius'' is a historically paraphyletic genus of platypterygiine ichthyosaur from the Cretaceous period. It was historically used as a wastebasket taxon, and most species within ''Platypterygius'' likely are undiagnostic at the genus ...
''. However, all recent
cladistic
Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...
analyses found that ''Maiaspondylus'' is a valid genus of ophthalmosaurid. Patrick S. Druckenmiller and Erin E. Maxwell (2010) found it to be most closely related to ''"
Platypterygius
''Platypterygius'' is a historically paraphyletic genus of platypterygiine ichthyosaur from the Cretaceous period. It was historically used as a wastebasket taxon, and most species within ''Platypterygius'' likely are undiagnostic at the genus ...
" americanus'', which probably do not belong to the genus ''Platypterygius''.
Etymology
''Maiaspondylus'' was named by Erin E. Maxwell and Michael W. Caldwell in 2006 and the
type species
In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specime ...
is ''Maiaspondylus lindoei''. The generic name is derived from ''maia'' (μαία),
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
for "caring mother" and ''spondylos'' (σπόνδυλος), Greek for "vertebra". The generic name named in reference to the unique specimen, UALVP 45639, that composed of two embryos agglutinated to eight articulated
vertebra
The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...
e of an adult (within its body cavity), presumably the mother. Maxwell and Caldwell (2003) suggested that this specimen proves that ''Maiaspondylus'' was
viviparous
Among animals, viviparity is development of the embryo inside the body of the parent. This is opposed to oviparity which is a reproductive mode in which females lay developing eggs that complete their development and hatch externally from the ...
, giving live birth. These embryos are the geologically youngest and the physically smallest known ichthyosaur embryos. The specific name honors the Geology Museum of the University of Alberta technician Allan Lindoe for discovering, collecting and preparating the specimens.
A study on the anatomy and phylogenetic relationships of ''Maiaspondylus lindoei'', ''"
Ophthalmosaurus
''Ophthalmosaurus'' (meaning "eye lizard" in Greek) is an ichthyosaur of the Jurassic period (165–150 million years ago). Possible remains from the Cretaceous, around 145 million years ago, are also known. It was a relatively medium-sized ich ...
" cantabrigiensis'' and ''"
Platypterygius
''Platypterygius'' is a historically paraphyletic genus of platypterygiine ichthyosaur from the Cretaceous period. It was historically used as a wastebasket taxon, and most species within ''Platypterygius'' likely are undiagnostic at the genus ...
" ochevi'' was published by Zverkov & Grigoriev (2020), who transfer ''"O". cantabrigiensis'' to the genus ''Maiaspondylus'', and consider ''"P. ochevi'' to be a junior synonym of ''M. cantabrigiensis''.
Phylogeny
The following cladogram shows a possible phylogenetic position of ''Maiaspondylus'' in Ophthalmosauridae according to the analysis performed by Zverkov and Jacobs (2020).