The Portland Formation is a geological formation in Connecticut and Massachusetts in the northeastern United States.Portland Formation - USGS It dates back to the Early Jurassic period.Weishampel et al., 2004, pp.530–532 The formation consists mainly of sandstone laid down by a series of lakes (in the older half of the formation) and the floodplain of a river (in the younger half). The sedimentary rock layers representing the entire Portland Formation are over thick and were formed over about 4 million years of time, from the Hettangian age (lower half) to the late Hettangian and Sinemurian ages (upper half).Olsen, P.E. (2002).
In 2016, the paleontologist Robert E. Weems and colleagues suggested the Portland Formation should be elevated to a geological group within the Newark Supergroup (as the Portland Group), and thereby replacing the former name "Agawam Group". They also reinstated the Longmeadow Sandstone as a formation (within the uppermost Portland Group); it had earlier been considered identical to the Portland Formation.
Vertebrate paleofauna Dinosaur coprolites are known from the formation. This formation and the underlying East Berlin Formation are well-known for its numerous well-preserved dinosaur tracks, made by trackmakers including ornithischians, theropods, and sauropodomorphs, which are preserved at sites such as Dinosaur Footprints Reservation. Other tracks are also known representing animals such as pseudosuchians, turtles, and temnospondyls.
Dinosaurs Genus Species Location Stratigraphic position Material Notes Images Anomoepus Olsen, Rainforth (2003). A. sp. Massachusetts Connecticut Hundreds of ornithischian footprints and trackways. Tracks made by small Ornithischians. Eubrontes E. sp. Massachusetts Connecticut Many theropod footprints and trackways. Tracks made by medium to large sized theropods likely similar to Dilophosaurus. Grallator G. sp. Massachusetts Connecticut Many theropod footprints and trackways. Tracks made by small to medium sized theropods likely similar to Coelophysis. Otozoum Olsen, Whiteside (2005). O. sp Massachusetts Connecticut Many sauropodomorph trackways. Tracks made by medium sized Sauropodomorphs. Likely made by animals such as Anchisaurus. Anchisaurus A. polyzelus Connecticut Massachusetts Several specimens. A relatively small basal Sauropodomorph. Many Otozoum tracks in the formation that may belong to Anchisaurus could have been made by potentially even larger specimens of the genus. Podokesaurus P. holyokensis Massachusetts Partial postcranial skeleton."Table 3.1," in Weishampel et al., 2004, p.48 A coelophysoid theropod. The only specimen was destroyed in a fire. Neotheropoda indet.McMenamin, M. (2021). Large neotheropod from the Lower Jurassic of Massachusetts. AcademiaLetters, Article 3591. by the author — Open Access — Distributed under CC BY 4.0indeterminateMassachusettsPartial humerus. Estimated to have been 9 meters long, and possibly a semiaquatic piscivore. Theropoda indet.indeterminateConnecticutTwo specimens and tracks attributed to "Anchisauripus"The animal was noted as being similar to Coelophysis as well as being slightly larger than some of the largest specimens attributed to Coelophysis.
Non-dinosaur archosaurs Genus Species Location Stratigraphic position Material Notes Images Stegomosuchus S. longipesHine's Quarry, Longmeadow Partial postcranial skeleton. Originally Stegomus. A small armored "protosuchian" crocodyliform. Pterosauria indet,indeterminate South Hadley, Massachusetts Partial wrist bone and tooth. Non-pterodactyloid pterosaur estimated to have a wingspan of 40 cm. Fish Genus Species Location Stratigraphic position Material Notes ImagesAcentrophorusA. chicopensisMaterial initially referred to the genus Acentrophorus. Most researchers consider the species distinct from Acentrophorus.RedfieldiusR. gracilisThe last surviving redfieldiiform fish.SemionotusS. sp.A semionotid fish.
Invertebrate paleofauna Insects Genus Species Location Stratigraphic position Material Notes ImagesHolcopteraH. schlotheimi A coptoclavid beetle known with distinct color pattern.H. giebeliOrthopteraindeterminateBlattariaindeterminatePolyphagaindeterminateAn indeterminate polyphagan larvae. Similar to Mormolucoides but larger.
See also List of dinosaur-bearing rock formations Newark Supergroup Paleontology in Connecticut Paleontology in Massachusetts
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