Unranked clade
Valid Extinct

Merriamosauria

Motani 1999

Merriamosauria is an extinct clade of ichthyosaurs. It was named by Ryosuke Motani in his 1999 analysis of the relationships of ichthyopterygian marine reptiles and was defined in phylogenetic terms as a stem-based taxon including "the last common ancestor of Shastasaurus pacificus and Ichthyosaurus communis, and all of its descendants." The name honours John Campbell Merriam. Based on this definition, Merriamosauria includes most ichthyosaurs except for several Triassic groups such as the clade Mixosauria, the family Cymbospondylidae, and perhaps the family Toretocnemidae. Merriamosaurs are characterized by features in their pectoral girdles and limb bones, including an extensive connection between the scapula and the coracoid bone, the absence of the first metacarpal and the absence of a pisiform bone.

Temporal range
Triassic
Jurassic
Cretaceous
Paleogene
Neogene
252 201 145 66 0 Ma
PBDB occurrences
52
Group
Ichtyosaures
Carnivore nektonic Marine
Merriamosauria
click to enlarge
Partial skull of Shastasaurus pacificus (UCMP 9017) from the Late Triassic of California, USA, in (A) lateral, (B) dorsal, and (C) anterolateral view. Based on this skull, Shastasaurus has repeatedly been reconstructed with a long, tooth-bearing rostrum. However, note the slenderness of the lower jaw (B, C) and the strong anterior taper of the snout (B), both of which are more consistent with the abbreviated and toothless snout of Shastasaurus liangae comb. nov. than with the traditional long-snouted reconstruction of this skull (as, e.g., in references [22] and [23]). © P. Martin Sander1*, Xiaohong Chen2, Long Cheng2, Xiaofeng Wang2 · CC BY 2.5 · Wikimedia
PBDB ↗ Wikipedia ↗
Classification
Ichthyosauria Unranked clade
›
Hueneosauria Unranked clade
›
Merriamosauria Unranked clade
Fossil sites 52 geolocated sites
Distribution
Top countries
🇺🇸 United States
13
🇨🇳 China
11
🇨🇦 Canada
7
🇫🇷 France
6
🇸🇯 SJ
4
🇨🇭 Switzerland
3
🇲🇽 Mexico
2
🇮🇹 Italy
2
🇳🇿 New Zealand
1
🇩🇪 Germany
1
Geological formations
Hosselkus
6
Pardonet
6
Xiaowa
5
Falang
3
Luning
3
Monte San Giorgio bituminous shales
2
Hosselkus Limestone
2
Antimonio
2
Wayao
2
Kössen
2
Temporal distribution
Hettangian (201.4–199.5 Ma)
1
Rhaetian (205.7–201.4 Ma)
9
Norian (227.3–205.7 Ma)
17
Carnian (237–227.3 Ma)
15
Ladinian (241.464–237 Ma)
4
Anisian (246.7–241.464 Ma)
4
Olenekian (249.9–246.7 Ma)
2
Images 1
Bibliography
Original description
R. Motani. 1999. Phylogeny of the Ichthyopterygia. Journal of Vertebrate Paleontology 19(3):473-496 DOI ↗
Bibliography (37)
D. R. Lomax, P. de la Salle, and M. Perillo, J. Reynolds, R. Reynolds, J. F. Waldron. 2024. The last giants: New evidence for giant Late Triassic (Rhaetian) ichthyosaurs from the UK. PLoS One 19(4):e0300289 DOI ↗
P. M. Sander, P. R. Pérez De Villar, and H. Furrer, T. Wintrich. 2022. Giant Late Triassic ichthyosaurs from the Kössen Formation of the Swiss Alps and their paleobiological implications. Journal of Vertebrate Paleontology 41(6):e2046017 DOI ↗
D.-Y. Jiang, R. Motani, and A. Tintori, O. Rieppel, C. Ji, M. Zhou, X. Wang, H. Lu, Z.-G. Li. 2020. Evidence supporting predation of 4-m marine reptile by Triassic megapredator. iScience DOI ↗
D. Konietzko-Meier, J. D. Werner, and T. Wintrich, P. M. Sander. 2019. A large temnospondyl humerus from the Rhaetian (Late Triassic) of Bonenburg (Westphalia, Germany) and its implications for temnospondyl extinction. Journal of Iberian Geology 45(2):287-300 DOI ↗
H. Lu, D.-Y. Jiang, and R. Motani, P.-G. Ni, Z.-Y. Sun, A. Tintori, S.-Z. Xiao, M. Zhou, C. Ji, W.-F. Fu. 2018. Middle Triassic Xingyi Fauna: Showing turnover of marine reptiles from coastal to oceanic environments. Palaeoworld 27(1):107-116 DOI ↗
C. Dal Sasso, G. Insacco, and AA Chiarenza, D. Di Franco, A. Reitano. 2014. First record of Ichthyosaurs in Sicily (Upper Triassic of Monte Scalpello, Catania province). Rivista Italiana di Paleontologia e Stratigrafia 120(1):71-82 DOI ↗
V. Fischer, H. Capetta, and P. Vincent, G. Garcia, S. Goolaerts, J. E. Martin, D. Roggero, X. Valentin. 2014. Ichthyosaurs from the French Rhaetian indicate a severe turnover across the Triassic-Jurassic boundary. Naturwissenschaften 101:1027-1040 DOI ↗
N. B. Fröbisch, J. Fröbisch, and P. M. Sander, L. Schmitz, O. Rieppel. 2013. Macropredatory ichthyosaur from the Middle Triassic and the origin of modern trophic networks. Proceedings of the National Academy of Sciences 110(4):1393-1397 DOI ↗
C. Ji, D.-Y. Jiang, and R. Motani, W.-C. Hao, Z.-Y. Sun, T. Cai. 2013. A new juvenile specimen of Guanlingasaurus (Ichthyosauria, Shastasauridae) from the Upper Triassic of southwestern China. Journal of Vertebrate Paleontology 33(2):340-348 DOI ↗
M. W. Maisch. 2010. Phylogeny, systematics, and origin of the Ichthyosauria - the state of the art. Palaeodiversity 3:151-214
Q.-H. Shang and C. Li. 2009. On the occurrence of the ichthyosaur Shastasaurus in the Guanling biota (Late Triassic), Guizhou, China. Vertebrata PalAsiatica 47(3):178-193
X. Wang, G. H. Bachmann, and H. Hagdorn, P. M. Sanders, G. Cuny, X. Chen, C. Wang, L. Chen, L. Cheng, F. Meng, G. Xu. 2008. The Late Triassic black shales of the Guanling area, Guizhou province, south-west China: a unique marine reptile and pelagic crinoid fossil lagerstätte. Palaeontology 51(1):27-61
X.-H. Chen, L. Cheng, and P. M. Sander. 2007. A new species of Callawayia (Reptilia: Ichthyosauria) from the Late Triassic in Guanling, Guizhou. Geology in China 34(6):974-982
L. Cheng, O. Wings, and X. Chen, P. M. Sander. 2006. Gastroliths in the Triassic ichthyosaur Panjiangsaurus from China. Journal of Paleontology 80(3):583-588
M. W. Maisch, X.-R. Pan, and Z.-Y. Sun, T. Cai, D.-P. Zhang, J.-L. Xie. 2006. Cranial osteology of Guizhouicthyosaurus tangae (Reptilia: Ichthyosauria) from the Upper Triassic of China. Journal of Vertebrate Paleontology 26(3):588-597 DOI ↗
E. L. Nicholls and M. Manabe. 2004. Giant ichthyosaurs of the Triassic - a new species of Shonisaurus from the Pardonet Formation (Norian: Late Triassic) of British Columbia. Journal of Vertebrate Paleontology 24(4):838-849 DOI ↗
M. Dalla Vecchia and M. Avanzini. 2002. New findings of isolated remains of Triassic reptiles from Northeastern Italy. Bollettino della Societa Paleontologica Italiana 42(2-3):215-235
M. W. Maisch and A. T. Matzke. 2002. Observations on Triassic ichthyosaurs. Part IX. The first associated skeletal remains of Merriamosaurus n. g. (Ichthyosauria, Lower Triassic) and their bearing on the systematic position of the Omphalosauria. Neues Jahrbuch fur Geologie und Palaontologie, Abhandlungen 226(1):59-94 DOI ↗
E. L. Nicholls and M. Manabe. 2001. A new genus of ichthyosaur from the Late Triassic Pardonet Formation of British Columbia: bridging the Triassic-Jurassic gap. Canadian Journal of Earth Sciences 38:983-1002 DOI ↗
M. W. Maisch and A. T. Matzke. 2000. The Ichthyosauria. Stuttgarter Beitrage zur Naturkunde, Serie B (Geologie und Palaontologie) 298:1-159
P. M. Sander. 2000. Ichthyosauria: their diversity, distribution and phylogeny. Palaeontologische Zeitschrift 74(1/2):1-35 DOI ↗
E. L. Nicholls, D. B. Brinkman, and X.-C. Wu. 1998. A new archosaur from the Upper Triassic Pardonet Formation of British Columbia. Canadian Journal of Earth Sciences 35:1134-1142 DOI ↗
M.-M. Chang and F. Jin. 1996. Mesozoic fish faunas of China. Mesozoic Fishes - Systematics and Paleoecology 1:461-478
S. G. Lucas and C. M. González-León. 1995. Ichthyosaurs from the Upper Triassic of Sonora and the biochronology of Triassic ichthyosaurs. Geological Society of America Special Paper 301:17-20 DOI ↗
C. Mcgowan. 1994. A new species of Shastasaurus (Reptilia: Ichthyosauria) from the Triassic of British Columbia: the most complete exemplar of the genus. Journal of Vertebrate Paleontology 14(2):168-179 DOI ↗
J. M. Mazin and P. M. Sander. 1993. Palaeobiogeography of the Early and Late Triassic ichthyopterygia. Paleontologia Lombarda 2:93-107
V. de Buffrenil and J. M. Mazin. 1990. Bone histology of the ichthyosaurs: comparative data and functional interpretation. Paleobiology 16(4):435-447
J. M. Callaway and J. A. Massare. 1989. Shastasaurus altispinus (Ichthyosauria, Shastasauridae) from the Upper Triassic of the El Antimonio District, northwestern Sonora, Mexico. Journal of Paleontology 63(6):930-939 DOI ↗
J. A. Hogler and R. A. Hanger. 1989. A new condrophorine (Hydrozoa, Velellidae) from the Upper Triassic of Nevada. Journal of Paleontology 63(2):249-251 DOI ↗
W. N. Orr and K. T. Katsura. 1985. Oregon's oldest vertebrates [Ichthyosauria(Reptilia)]. Oregon Geology 47(7):75-77
J. D. Campbell. 1965. New Zealand Triassic saurians. New Zealand Journal of Geology and Geophysics 8(3):505-509 DOI ↗
J. C. Merriam. 1908. Triassic Ichthyosauria. Memoirs of the University of California 1(1):1-155 DOI ↗
H.-E. Sauvage. 1907. Vertébrés [Vertebrates]. Note sur L'Infralias de Provenchères-sur-Meuse
J. C. Merriam. 1906. Notes on the osteology of the thalattosaurian genus Nectosaurus. University of California Publications, Bulletin of the Department of Geology 5(13):217-223
J. C. Merriam. 1902. Triassic Ichthyopterygia from California and Nevada. University of California Publications Bulletin of the Department of Geology 3(4):63-108
J. C. Merriam. 1895. On some Reptilian Remains from the Triassic of Northern California. American Journal of Science 50(295):55 DOI ↗
H.-E. Sauvage. 1883. Recherches sur les reptiles trouvés dans l'étage rhétien des environs d'Autun [Research on the reptiles found in the Rhaetian stage of the environs of Autun]. Annales des Sciences Géologiques 14(3):1-44