Open Paleo

Telmatosaurus

Nopcsa, 1903 TEL-ma-to-SAWR-us

From Greek telma/telmat-, "swamp" or "marsh", combined with Greek sauros, "lizard" — means "marsh lizard"

72.2–66.0 million years ago Maastrichtian, Late Cretaceous
Late Cretaceous stages

Telmatosaurus is a genus of basal hadrosauromorph dinosaur from the Late Cretaceous of Romania. It was relatively small for its group, measuring approximately 5 m (16 ft) in length and 600 kg (1,300 lb) in body mass, which has been explained as an instance of insular dwarfism.

Under dispute

Telmatosaurus transsylvanicus was historically treated as the most basal hadrosaurid (Weishampel and colleagues, 1993), but recent analyses place it among the derived non-hadrosaurid hadrosauromorphs, outside Hadrosauridae (Xing and colleagues, 2014; Tsogtbaatar and colleagues, 2019). Analyses on several matrices recover it as the sister taxon of Tethyshadros (Xing and colleagues, 2014; Lockwood and colleagues, 2021), while others place the two at successive nodes below Hadrosauridae (Prieto-Márquez and colleagues, 2013). Magyar and colleagues (2026) name the group, with Kryptohadros, as the clade Telmatosauridae.

Diagnosis

  1. Strong development of tubera basioccipitalia, completely covered by basisphenoid swellings, distinguishing it from hadrosaurids
  2. Basipterygoid apophyses connected by high perpendicular transverse wall unique among ornithopods
  3. Elongated nasal cavity with greatly extended premaxillaries reaching backward beyond lacrimal nearly to orbit
  4. Dentale forms U-shaped connection with opposite mandibular ramus, distinguished from Camptosaurs by sharp inward curve
  5. Lower jaw teeth with simple notched margins and lack of lateral surface, distinguishing from L. Hilli specimen
  6. Lower jaw teeth bearing slightly elevated ridge on inner enamel surface with nodular thickening at mid-height

Species

Telmatosaurus transsylvanicus (Nopcsa, 1900)

Type species

First named as Limnosaurus transsylvanicus

Named for Transylvania, the region of Romania where the holotype skull was found, with the Latin suffix '-icus' meaning 'of' or 'pertaining to'.

Holotype
BMNH R3386 , Natural History Museum
Material
Almost complete skull (49 cm length) with mandible, fragments of upper and lower jaws from smaller individuals, basis cranii fragment
Horizon
Sânpetru Formation, Maastrichtian, Late Cretaceous , 72.2–66.0 million years ago
Locality
Bonebed 1, along the Sibișel Valley near the village of Sânpetru, Hunedoara, Romania

Synonyms

  • Orthomerus transsylvanicus reassigned

    Nopcsa (1915) transferred Telmatosaurus transsylvanicus into the pre-existing genus Orthomerus Seeley, 1883 as Orthomerus transsylvanicus, an assignment followed by Romer in Romer's reptile reviews but rejected by modern workers. The species-level reassignment applies to T. transsylvanicus only — the genus Orthomerus remains a separate valid (though dubious) name (per Olshevsky 1991; Madzia and colleagues 2019).

Synonyms of the genus

Name Type Reason
Hecatasaurus junior objective Proposed by Brown (1910) to replace the preoccupied Limnosaurus, overlooking Telmatosaurus, the replacement name Nopcsa (1903) had already given it.
Limnosaurus preoccupied Name preoccupied by Limnosaurus (Crocodilia).

Notable specimens

  • LPB (FGGUB) R.1305

    Laboratory of Paleontology, Faculty of Geology and Geophysics, University of Bucharest pathology

    A juvenile bearing a large benign ameloblastoma tumor on its lower jaw, the first occurrence of this tumor type in the fossil record, indicating susceptibility to such tumors is a deep-rooted feature of vertebrates. The animal died before reaching adulthood.

    Dumbravă et al. (2016)

References

  1. Dumbravă, M. D.; Rothschild, B. M.; Weishampel, D. B.; Csiki-Sava, Z.; Andrei, R. A.; Acheson, K. A.; Codrea, V. A. (2016). A dinosaurian facial deformity and the first occurrence of ameloblastoma in the fossil record. Scientific Reports 6(1): 29271. Springer Science and Business Media LLC. doi:10.1038/srep29271 dumbravă2016a
  2. Nopcsa, F. (1900). Dinosaurierreste aus Siebenbürgen (Schädel von Limnosaurus transsylvanicus nov. gen. et spec.) [Dinosaur remains from Transylvania (skull of Limnosaurus transsylvanicus n. gen. et spec.)]. Denkschriften der Kaiserlichen Akademie der Wissenschaften. Mathematisch-Naturwissenschaftliche Classe 68: 555-591.

    In German. Original description of the material as Limnosaurus transsylvanicus; the genus name was preoccupied and renamed Telmatosaurus by Nopcsa (1903).

    nopcsa1900a
  3. Nopcsa, B. F. (1903). Telmatosaurus, new name for the dinosaur Limnosaurus. Geological Magazine, decade 4 10: 94-95. nopcsa1903a
  4. Brown, B. (1910). The Cretaceous Ojo Alamo beds of New Mexico with description of the new dinosaur genus Kritosaurus. Bulletin of the American Museum of Natural History 28(24): 267-274.

    Proposes Hecatasaurus to replace Limnosaurus.

    brown1910a
  5. Paul, G. S. (2024). The Princeton Field Guide to Dinosaurs (3rd ed.). Princeton University Press.

    Source of the appearance features.

    paul2024a
  6. Tsogtbaatar, K.; Weishampel, D. B.; Evans, D. C.; Watabe, M. (2019). A new hadrosauroid (Dinosauria: Ornithopoda) from the Late Cretaceous Baynshire Formation of the Gobi Desert (Mongolia). PLOS ONE 14(4): e0208480. Public Library of Science (PLoS). doi:10.1371/journal.pone.0208480

    Described new hadrosauroid, placing Telmatosaurus among derived non-hadrosaurid hadrosauromorphs.

    tsogtbaatar2019a
  7. Magyar, J.; Ősi, A.; Csiki-Sava, Z.; Budai, S.; Botfalvai, G. (2026). New early Maastrichtian 'duck-billed' dinosaur from Hațeg Basin (Densuș-Ciula Formation, Romania) documents an endemic clade of non-hadrosaurid hadrosauroids in the south-eastern Late Cretaceous European Archipelago. Journal of Systematic Palaeontology 24(1): 2607800. Informa UK Limited. doi:10.1080/14772019.2025.2607800

    Described new Hațeg duck-billed dinosaur, grouping Telmatosaurus with Tethyshadros and Kryptohadros.

    magyar2026a
  8. Weishampel, D. B.; Norman, D. B.; Grigorescu, D. (1993). Telmatosaurus transsylvanicus from the Late Cretaceous of Romania: the most basal hadrosaurid dinosaur. Palaeontology 36(2): 361-385.

    Described Telmatosaurus transsylvanicus and argued it was the most basal known hadrosaurid

    weishampel1993a
  9. Olshevsky, G. (1991). A revision of the parainfraclass Archosauria Cope, 1869, excluding the advanced Crocodylia. Mesozoic Meanderings 2: 1-196.

    Treated Orthomerus as a separate valid though dubious name.

    olshevsky1991a
  10. Madzia, D.; Jagt, J. W. M.; Mulder, E. W. A. (2019). Osteology, phylogenetic affinities and taxonomic status of the enigmatic late Maastrichtian ornithopod taxon Orthomerus dolloi (Dinosauria, Ornithischia). Cretaceous Research 108: 104334. Elsevier BV. doi:10.1016/j.cretres.2019.104334

    Treated Orthomerus as separate from Telmatosaurus.

    madzia2019a
  11. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Ornithischians. Princeton University Press.

    Treats Telmatosaurus as a non-hadrosaurid hadrosauromorph.

    jones2026a
  12. Nopcsa, B. F. (1915). Die Dinosaurier der siebenbürgischen Landesteile Ungarns [The Dinosaurs of the Transylvanian Territories of Hungary]. Mitteilungen aus dem Jahrbuche der Königlich Ungarischen Geologischen Reichsanstalt 23: 1-26. nopcsa1915a
  13. Xing, H.; Wang, D.; Han, F.; Sullivan, C.; Ma, Q.; He, Y.; Hone, D. W. E.; Yan, R.; Du, F.; Xu, X. (2014). A New Basal Hadrosauroid Dinosaur (Dinosauria: Ornithopoda) with Transitional Features from the Late Cretaceous of Henan Province, China. PLoS ONE 9(6): e98821. Public Library of Science (PLoS). doi:10.1371/journal.pone.0098821

    Recovered Telmatosaurus and Tethyshadros as sister taxa.

    xing2014a
  14. Lockwood, J. A. F.; Martill, D. M.; Maidment, S. C. R. (2021). A new hadrosauriform dinosaur from the Wessex Formation, Wealden Group (Early Cretaceous), of the Isle of Wight, southern England. Journal of Systematic Palaeontology 19(12): 847-888. Informa UK Limited. doi:10.1080/14772019.2021.1978005

    Recovered Telmatosaurus and Tethyshadros as sister taxa, outside Hadrosauridae.

    lockwood2021a
  15. Prieto-Márquez, A.; Dalla Vecchia, F. M.; Gaete, R.; Galobart, À. (2013). Diversity, Relationships, and Biogeography of the Lambeosaurine Dinosaurs from the European Archipelago, with Description of the New Aralosaurin Canardia garonnensis. PLoS ONE 8(7): e69835. Public Library of Science (PLoS). doi:10.1371/journal.pone.0069835

    Recovered Telmatosaurus and Tethyshadros at successive nodes below Hadrosauridae.

    prieto-márquez2013a