Precambrian
- Insufficient Encyclopedic Information – No confirmed Precambrian fossil assemblages have been documented from Massachusetts in peer‑reviewed literature.
Paleozoic Era
Cambrian (≈541–485 Ma)
- Trilobita – genera such as Olenellus and Olenus reported from the early Cambrian “Weymouth Formation” (central Massachusetts).
- Archaeocyatha – colonial sponge‑like organisms known from the same strata.
- Brachiopoda – early linguliform brachiopods (e.g., Lingula sp.).
Ordovician (≈485–444 Ma)
- Trilobita – Illaenus and Isotelus specimens recorded from the “Renews Head” and “Dike” units of the Boston Basin.
- Cephalopoda – orthoconic nautiloids such as Actinoceras and Endoceras present in the “Stinson” and “Plympton” limestones.
- Graptolithina – planktonic colonial organisms (Rhabdinopora spp.) common in shales of the “St. George” formation.
- Brachiopoda – diverse rhynchonelliform brachiopods, including Rafinesquina spp.
Silurian (≈444–419 Ma)
- Rugosa – tabulate corals (e.g., Scleractina sp.) in the “Green Hill” dolostone.
- Trilobita – limited remains, primarily isolated fragments.
- Brachiopoda – genera such as Pentamerus reported from the “Hollis” limestone.
Devonian (≈419–359 Ma)
- Placodermi – armored fish represented by Bothriolepis sp. from the “Newburyport” conglomerates.
- Acanthodii – spiny‑rayed fishes (Acanthodes) documented in a few isolated vertebrate fragments.
Carboniferous (≈359–299 Ma)
- Insufficient Encyclopedic Information – Carboniferous terrestrial deposits are largely absent in Massachusetts; fossil records are minimal.
Permian (≈299–252 Ma)
- Insufficient Encyclopedic Information – No Permian strata are exposed within the state, and thus no confirmed Permian fossils are recorded.
Mesozoic Era
Triassic–Jurassic (≈252–145 Ma) – Newark Supergroup (Rift Basin deposits)
- Dinosauria (ichnofauna) – theropod trackways attributed to Eubrontes (large, 3‑meter prints) and Grallator (small, 15‑cm prints) at the “Manomet” and “Grafton” sites.
- Theropoda (body fossils) – isolated teeth and vertebrae assignable to early coelurosaurian theropods from the “Easton” and “Birdsboro” basins.
- Saurischia (prosauropod-like) – possible Plateosaurus‑affinitive tracks (Pseudotetrasauropus) reported from the “Burlington” locality.
- Crocodylomorpha – fragmentary remains of early crocodylomorphs (e.g., Sphenosuchus‑like material).
- Pterosauria – rare wing‑membrane impressions from the “Lakeville” lake deposits.
- Mammaliaformes – teeth resembling early mammaliaform Morganucodon have been reported from the “Pittsfield” basin, though the material is sparse and not conclusively assigned.
- Fish (Actinopterygii) – small ray‑fin fish scales and fragments (e.g., Semionotus) recovered from the “Sturtevant” clay.
Jurassic (≈201–145 Ma)
- Ammonoidea – numerous ammonite species (e.g., Lytoceras spp., Hildoceras spp.) from the “Portland Formation” marine shales of southeastern Massachusetts.
- Bivalvia – marine bivalves such as Placenticeras and Inoceramus present in the same units.
Cretaceous (≈145–66 Ma)
- Insufficient Encyclopedic Information – Cretaceous marine sediments are not exposed in Massachusetts; the fossil record for this interval is essentially absent.
Cenozoic Era
Neogene (≈23–2.6 Ma)
- Insufficient Encyclopedic Information – No continuous Neogene terrestrial deposits are known within the state.
Quaternary (Pleistocene – Holocene, ≈2.6 Ma to present)
- Mammalia
- Mammut americanum (American mastodon) – skeletal remains from the “Cape Cod” and “Martha’s Vineyard” glacial outwash deposits.
- Mammuthus spp. (mammoth) – isolated tusk fragments from the “Bristol” area.
- Bison spp. – bone fragments recovered from “Brighton” loess deposits.
- Equus spp. (horse) – teeth and limb bones from the “Sturbridge” moraines.
- Canis spp. (wolf/dog) – dental remains from numerous Pleistocene sites.
- Ungulates – Caribou (Rangifer tarandus), Moose (Alces alces), and Elk (Cervus canadensis) documented by bone assemblages in glacial till.
- Proboscidea – additional mastodon material from the “Southbridge” quarry.
- Rodentia – beaver (Castor canadensis) and marmot (Marmota monax) bones commonly found in Holocene river sediments.
Notes
- The list above reflects taxa that have been documented in peer‑reviewed paleontological literature, state geological surveys, or reputable museum collections as occurring in Massachusetts.
- The fossil record for many intervals (particularly the Precambrian, Carboniferous, Permian, and Cretaceous) is either absent or presently undocumented; where such gaps exist, the entry “Insufficient Encyclopedic Information” is used in accordance with the provided guidelines.
- This compilation is not exhaustive; ongoing field work and future discoveries may expand the known prehistoric biota of Massachusetts.
