Post by Infinity Blade on Mar 22, 2023 2:44:52 GMT 5
Saint Bathans mammal
A hypothetical illustration of the Saint Bathans mammal. © @ Nix Illustration->
Temporal range: Neogene; Early to Middle Miocene; Burdigalian (Altonian; ~19-16 Ma[1])
Scientific classification:
Life
Domain: Eukaryota
(unranked): Unikonta
(unranked): Opisthokonta
(unranked): Holozoa
(unranked): Filozoa
Kingdom: Animalia
Subkingdom: Eumetazoa
(unranked): Bilateria
Clade: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Clade: Olfactores
Clade: Craniata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Clade: Eugnathostomata
Clade: Teleostomi
Superclass: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Clade: Synapsida
Clade: Eupelycosauria
Clade: Sphenacodontia
Clade: Sphenacodontoidea
Order: Therapsida
Clade: Eutheriodonta
Suborder: Cynodontia
Clade: Epicynodontia
Infraorder: Eucynodontia
Parvorder: Probainognathia
Superfamily: Chiniquodontoidea
Clade: Prozostrodontia
Clade: Mammaliaformes
Class: Mammalia
Clade: Holotheria
Superlegion: Trechnotheria
Legion: Cladotheria
Sublegion: Zatheria
Infralegion: Tribosphenida
Clade: Theriiformes?
The Saint Bathans mammal is a currently unnamed species of mammal that lived in New Zealand during the Early to Middle Miocene from 19-16 million years ago. It is a part of the Saint Bathans fauna.[1]
Discovery:
In 1978, a previously unknown fossil fauna was discovered from the Manuherikia Group of South Island, New Zealand. This fauna was found in sediments that dated to the Early Miocene.[1]
Among the fauna were the remains of at least one species of terrestrial mammal represented by three specimens. These include two almost identical mandibular fragments and a femoral fragment, all belonging to mouse-sized animals. Although it has not been ruled out that these remains represent multiple species, the fact that they could all be the same single species and were the first terrestrial mammal remains known from New Zealand led to the original describers to tentatively refer to all three specimens as the same species.[1]
Description:
Based on the fragmentary remains currently known, the mandibles have a long fused symphysis, a procumbent medial incisor, and a dental formula of one incisor, one canine, and two double-rooted premolars (the teeth are not preserved; this is based on the presence and positioning of the alveoli).[1]
MNZ S.40958, a mandibular fragment. From [1]
One proximal femur fragment is also known. Its key characteristics include a round head on a very short, poorly-defined neck (less well defined than it is in monotremes), the head and neck being positioned slightly dorsomedially relative to the long axis of the femoral shaft, a lack of fused epiphyses and a fovea for the acetabular ligament on the femoral head, dense surface bone and sharp features indicating the individual was an adult at the time of death, a greater trochanter projecting laterally with little dorsal expansion, a pronounced trough that separates the head and neck from the greater trochanter, a shallow intertrochanteric fovea, and the lesser trochanter being on the postero- or ventromedial side of the shaft.[1]
MNZ S.42214, a proximal fragment of a right femur. From [1]
Phylogenetic placement:
Based on comparisons with the known remains of other mammalian and mammaliaform clades, the Saint Bathans mammal remains were concluded to belong to a single taxon. The mammal is believed to have been a basal mammal that is probably more derived than morganucodontans (which are not crown mammals), but more primitive than multituberculates and trechnotheres, while not being a monotreme or a eutriconodontan (although, positions within Monotremata or Theria have not been statistically rejected).[1]
Significance:
The Saint Bathans mammal is significant for two reasons. First, the apparently basal position of this mammal within the Mammalia suggests the presence of a long-surviving ghost lineage of previously unknown basal mammals in New Zealand, living from the Late Cretaceous to the Early Miocene. Like some other vertebrates living in New Zealand today, this mammal was a holdover from the Mesozoic, and its presence during the Early Miocene suggest that at least some of New Zealand remained during its Oligocene drowning event.[1]
Secondly, New Zealand is known for currently lacking a native non-volant terrestrial mammal fauna. Prior to human settlement, the only known mammals living on the island in recent times (i.e. the Quaternary) were three bat species. Otherwise, New Zealand during the Quaternary is considered to have been a “land of birds”. The presence of a non-volant terrestrial mammal living in New Zealand during the Early Miocene is evidence that the well-known “land of birds sans terrestrial mammals was a more recent development than previously thought (emerging in the last few million years instead of 82 million years as presumed), and that there have been considerable changes in the fauna since the Early Miocene.[1]
References:
[1] Worthy, T. H., Tennyson, A. J., Archer, M., Musser, A. M., Hand, S. J., Jones, C., ... & Beck, R. M. (2006). Miocene mammal reveals a Mesozoic ghost lineage on insular New Zealand, southwest Pacific. Proceedings of the National Academy of Sciences, 103(51), 19419-19423.
A hypothetical illustration of the Saint Bathans mammal. © @ Nix Illustration->
Temporal range: Neogene; Early to Middle Miocene; Burdigalian (Altonian; ~19-16 Ma[1])
Scientific classification:
Life
Domain: Eukaryota
(unranked): Unikonta
(unranked): Opisthokonta
(unranked): Holozoa
(unranked): Filozoa
Kingdom: Animalia
Subkingdom: Eumetazoa
(unranked): Bilateria
Clade: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Clade: Olfactores
Clade: Craniata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Clade: Eugnathostomata
Clade: Teleostomi
Superclass: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Clade: Synapsida
Clade: Eupelycosauria
Clade: Sphenacodontia
Clade: Sphenacodontoidea
Order: Therapsida
Clade: Eutheriodonta
Suborder: Cynodontia
Clade: Epicynodontia
Infraorder: Eucynodontia
Parvorder: Probainognathia
Superfamily: Chiniquodontoidea
Clade: Prozostrodontia
Clade: Mammaliaformes
Class: Mammalia
Clade: Holotheria
Superlegion: Trechnotheria
Legion: Cladotheria
Sublegion: Zatheria
Infralegion: Tribosphenida
Clade: Theriiformes?
The Saint Bathans mammal is a currently unnamed species of mammal that lived in New Zealand during the Early to Middle Miocene from 19-16 million years ago. It is a part of the Saint Bathans fauna.[1]
Discovery:
In 1978, a previously unknown fossil fauna was discovered from the Manuherikia Group of South Island, New Zealand. This fauna was found in sediments that dated to the Early Miocene.[1]
Among the fauna were the remains of at least one species of terrestrial mammal represented by three specimens. These include two almost identical mandibular fragments and a femoral fragment, all belonging to mouse-sized animals. Although it has not been ruled out that these remains represent multiple species, the fact that they could all be the same single species and were the first terrestrial mammal remains known from New Zealand led to the original describers to tentatively refer to all three specimens as the same species.[1]
Description:
Based on the fragmentary remains currently known, the mandibles have a long fused symphysis, a procumbent medial incisor, and a dental formula of one incisor, one canine, and two double-rooted premolars (the teeth are not preserved; this is based on the presence and positioning of the alveoli).[1]
MNZ S.40958, a mandibular fragment. From [1]
One proximal femur fragment is also known. Its key characteristics include a round head on a very short, poorly-defined neck (less well defined than it is in monotremes), the head and neck being positioned slightly dorsomedially relative to the long axis of the femoral shaft, a lack of fused epiphyses and a fovea for the acetabular ligament on the femoral head, dense surface bone and sharp features indicating the individual was an adult at the time of death, a greater trochanter projecting laterally with little dorsal expansion, a pronounced trough that separates the head and neck from the greater trochanter, a shallow intertrochanteric fovea, and the lesser trochanter being on the postero- or ventromedial side of the shaft.[1]
MNZ S.42214, a proximal fragment of a right femur. From [1]
Phylogenetic placement:
Based on comparisons with the known remains of other mammalian and mammaliaform clades, the Saint Bathans mammal remains were concluded to belong to a single taxon. The mammal is believed to have been a basal mammal that is probably more derived than morganucodontans (which are not crown mammals), but more primitive than multituberculates and trechnotheres, while not being a monotreme or a eutriconodontan (although, positions within Monotremata or Theria have not been statistically rejected).[1]
Significance:
The Saint Bathans mammal is significant for two reasons. First, the apparently basal position of this mammal within the Mammalia suggests the presence of a long-surviving ghost lineage of previously unknown basal mammals in New Zealand, living from the Late Cretaceous to the Early Miocene. Like some other vertebrates living in New Zealand today, this mammal was a holdover from the Mesozoic, and its presence during the Early Miocene suggest that at least some of New Zealand remained during its Oligocene drowning event.[1]
Secondly, New Zealand is known for currently lacking a native non-volant terrestrial mammal fauna. Prior to human settlement, the only known mammals living on the island in recent times (i.e. the Quaternary) were three bat species. Otherwise, New Zealand during the Quaternary is considered to have been a “land of birds”. The presence of a non-volant terrestrial mammal living in New Zealand during the Early Miocene is evidence that the well-known “land of birds sans terrestrial mammals was a more recent development than previously thought (emerging in the last few million years instead of 82 million years as presumed), and that there have been considerable changes in the fauna since the Early Miocene.[1]
References:
[1] Worthy, T. H., Tennyson, A. J., Archer, M., Musser, A. M., Hand, S. J., Jones, C., ... & Beck, R. M. (2006). Miocene mammal reveals a Mesozoic ghost lineage on insular New Zealand, southwest Pacific. Proceedings of the National Academy of Sciences, 103(51), 19419-19423.
