Smallmouth Sands Fossil Hunting

1865 – Waagen’s work formed part of the early scientific history of the Weymouth Kimmeridge Clay
Geological and palaeontological interest in the Kimmeridge Clay of the Weymouth district dates back to the nineteenth century, and Waagen’s work forms part of that early scientific foundation. This is one of the earliest milestones in the published history of the beds exposed at Smallmouth Sands.

1873 – pterosaur material from the Weymouth area was being named in the scientific literature
By the early 1870s, pterosaur material from the Weymouth Kimmeridge Clay had already entered the literature, including forms referred to Pterodactylus suprajurensis. This marks the beginning of the formal pterosaur discovery history tied to the Smallmouth Sands and Weymouth Kimmeridge Clay coast.

1874 – Owen named pterosaur material from the Weymouth Kimmeridge Clay
Richard Owen named pterosaur material from the Weymouth area, including fossils later referred to Rhamphorhynchus manselii, Rhamphorhynchus pleydelli, Pterodactylus manseli and Pterodactylus pleydelli. Although some of these old names are now considered doubtful, they remain important in the early discovery history of Smallmouth Sands.

1884 – Damon recorded varied “saurian remains” from the Smallmouth Sands locality
Damon’s work is one of the classic milestones for the locality because it records the presence of varied reptile material from the Smallmouth Sands area. This helped establish the site as more than just a shell bed and showed its potential for larger vertebrate fossils.

1889 – Lydekker documented turtles, crocodile material and other reptile remains from the Weymouth Kimmeridge Clay
By the late nineteenth century, work by Lydekker had expanded the known vertebrate importance of the Smallmouth Sands and Weymouth Kimmeridge Clay succession, including turtles and crocodilian material. This strengthened the site’s reputation as an important marine reptile locality.

1983 – ichthyosaur material from Smallmouth Sands was included in major work on British Upper Jurassic ichthyosaurs
Modern study of British Upper Jurassic ichthyosaurs included material from the Smallmouth Sands locality, helping confirm the importance of the site for marine reptile remains as well as pterosaurs.

1995 – Smallmouth Sands was described as one of the most diverse Kimmeridge Clay reptile assemblages in the world
Benton and Spencer described Smallmouth Sands as “one of the most diverse assemblages of Kimmeridge Clay reptiles anywhere in the world”. This was a major milestone in recognising the true palaeontological significance of the site.

1997 – an ichthyosaur paddle from Smallmouth Sands was documented
A partially articulated ichthyosaur paddle from the locality was described in the later twentieth century, showing that Smallmouth Sands could yield more than isolated bones and teeth. Finds like this helped confirm the importance of the site for better associated marine reptile material.

2010 onwards – Heather Middleton began systematically collecting pterosaur material from Smallmouth Sands
A major recent phase in the site’s history began when Heather Middleton started collecting pterosaur fossils from Smallmouth Sands in 2010. This long-term work would eventually help reveal just how rich the pterosaur assemblage really is.

2015 – published work highlighted the importance of Smallmouth Sands pterosaurs
By 2015, the locality’s pterosaur material had become important enough for detailed academic study, including doctoral work by O’Sullivan and research by Middleton and Wass. This marked the start of the modern scientific reassessment of the site’s pterosaur fauna.

2018 – a Smallmouth Sands ichthyosaur skull was documented by Heather Middleton
The publication of an ichthyosaur skull from the locality showed again that Smallmouth Sands continues to produce important marine reptile material in addition to its growing reputation for pterosaurs.

2019 – Mike Harvey began collecting pterosaur material from Smallmouth Sands
Mike Harvey joined the main recent collecting effort in 2019, adding to the growing modern collection that would later form the basis of the new major pterosaur study.

March 2025 – 533 Smallmouth Sands pterosaur specimens were donated to the Etches Collection
One of the biggest milestones in the site’s history came when 533 pterosaur specimens collected from Smallmouth Sands were donated to the Etches Collection Museum of Jurassic Marine Life in March 2025. Together with existing material in the Natural History Museum and Etches Collection, this created an unprecedented research resource for the site.

2025 – major new research showed Smallmouth Sands to be a particularly fossiliferous pterosaur locality
The recent Smallmouth Sands study reported a newly accessioned collection of over 500 pterosaur pieces and showed that the site preserves a diverse assemblage including rhamphorhynchines, ctenochasmatids, dsungaripterids, darwinopterans, germanodactylids and a possible anurognathid. This is one of the most important modern scientific developments for the locality and raises Smallmouth Sands to national importance for Late Jurassic pterosaurs.

Modern understanding – Smallmouth Sands is now recognised as one of the most important Kimmeridge Clay pterosaur localities in Britain
Today Smallmouth Sands is valued not only for its broader Kimmeridge Clay reptile fauna, including ichthyosaurs, plesiosaurs, crocodiles, turtles and occasional dinosaur material, but especially for its rich pterosaur assemblage. The recent work suggests that the low-erosion foreshore may still hold a substantial reservoir of pterosaur material, making the site one of the most exciting Late Jurassic vertebrate localities on the Dorset coast.

Turtles

Pelobatochelys blakei Seeley, 1875
Named by Harry Govier Seeley in 1875. This is one of the key Smallmouth Sands turtles and the GCR account lists its type material as BMNH 41235, 44177–8 and R2. The published source says the material consists of fragments of a chelonian carapace and notes that it is known only from Dorset, especially the Smallmouth section. The original finder is not given in the source used here.

Tropidemys langi Rütimeyer, 1873
Named in 1873 by Rütimeyer. At Smallmouth Sands this species is represented by isolated carapace elements tentatively identified by Lydekker. The GCR account treats it as one of the important early cryptodiran turtles from the site. No original finder is stated in the source.

Acichelys (Eurysternum) sp.
This turtle is present at Smallmouth Sands as several remains of carapace and limbs in the British Museum collections. The GCR account says the material has not been properly described. Because it is left in open nomenclature, there is no species-level name confirmed in the source. Finder not stated.

Plesiochelys sp.
Represented at Smallmouth Sands by some carapace remains and limb bones. The GCR account notes that material presently referred to this genus had previously been identified in different ways and still needs restudy. Finder not stated in the source.

Pelobatochelys sp.
Additional material from the locality has been left simply as Pelobatochelys sp. in the GCR faunal list. This means the genus is recognised, but the material has not been tied confidently to a named species beyond the type material of P. blakei. Finder not stated.

Crocodiles and other crocodylomorphs

Dakosaurus maximus (Plieninger, 1846)
Named by Plieninger in 1846. Smallmouth material assigned to this species consists largely of teeth according to the GCR account. The account adds that Dakosaurus was the larger, shorter-snouted metriorhynchid in the fauna, reaching around 4 metres in body length. The original finder of the Smallmouth material is not stated in the source.

Metriorhynchus sp.
Smallmouth Sands has yielded teeth, vertebrae, scutes and skull fragments assigned to Metriorhynchus. The GCR account describes it as a long-snouted marine crocodylomorph highly adapted for aquatic life, with shortened paddle-like limbs. No species-level identification is confirmed in the source. Finder not stated.

Steneosaurus sp.
Represented by teeth and some vertebrae, scutes and skull fragments. The GCR account describes Steneosaurus as a medium-sized, long-snouted marine fish-eating crocodile. The material is not taken further than genus level in the source. Finder not stated.

Pterosaurs

Rhamphorhynchus manselii (Owen, 1874)
Originally named by Richard Owen in 1874, with type specimen BMNH 41970 listed in the GCR account. The newer Smallmouth Sands pterosaur paper says this old name is now regarded as dubious and explains that many old Weymouth pterosaur names are probably just fragmentary rhamphorhynchid material rather than good separate species. No original finder is stated in the recent paper extract, only that the specimen is in the Natural History Museum collections.

Rhamphorhynchus pleydelli (Owen, 1874)
Also named by Owen in 1874, with type specimen BMNH 42378 listed by the GCR account. The recent pterosaur paper likewise treats the old species-level assignment as doubtful in modern terms, even though matching material exists in the newer Smallmouth collection. Original finder not stated in the source.

Rhamphorhynchus sp.
The GCR account lists additional pterosaur material from Smallmouth simply as Rhamphorhynchus sp. The new pterosaur paper strongly supports the presence of average-sized rhamphorhynchines at the site and suggests they were common in the assemblage. The modern collecting phase began with Heather Middleton in 2010, later joined by Mike Harvey in 2019 and Casey Rich in 2021, but the older museum material predates those finds.

Pterodactylus suprajurensis Sauvage, 1873
This old name appears in the historical Smallmouth/Weymouth pterosaur record. The recent pterosaur paper notes that such old species-level assignments are now considered doubtful and that the material probably belongs more broadly among rhamphorhynchids or other pterosaurs rather than a securely valid named species from Smallmouth. Finder not stated.

Ornithocheirus sp.
The recent pterosaur paper notes that partial elements from the older Weymouth material had been assigned to Ornithocheirus sp. in the past. This should now be treated cautiously, as the paper stresses that many of these historic names are doubtful. Finder not stated.

Dinosaurs

Pelorosaurus humerocristatus (Hulke, 1874)
Named by John Whitaker Hulke in 1874 from a very large left humerus originally about 1.5 m long. The GCR account says the type specimen is BMNH 44635 and notes that Hulke described it as a very large saurian limb-bone for progression on land. The specimen was enclosed in large septarian masses, which suggests it came from one of Damon’s septarian beds or from Portland Harbour. The original finder is not stated in the source.

Dacentrurus armatus Owen, 1875
Represented at Smallmouth Sands by a stegosaur vertebra, BMNH 15910, referred to this species. The GCR account notes that the short neural spine of the vertebra is diagnostic for the species. Original finder not stated in the source.

Megalosauridae indet.
A megalosaurid jaw fragment was dredged up in Portland Harbour in the 1980s, with associated ammonites indicating the autissiodorensis Zone. This is a key dinosaur record for the Smallmouth / Portland Harbour area, but the source does not name a species. The published source attributes the record to Powell, 1988, but does not give the finder’s name.

‘Hypsilophodontid’ indet.
The GCR account lists a hypsilophodontid record from Weymouth/Smallmouth based on a dentary tooth described by Galton. It later notes that Galton himself tentatively questioned whether the locality assignment might be wrong because of similarity to a Late Cretaceous tooth from Wyoming. So this is best treated as a doubtful historical record rather than a secure named species from Smallmouth.

Plesiosaurs and pliosaurs

Kimmerosaurus langhami Brown, 1981
Named by David Brown in 1981. The GCR account says BMNH R1798, a partial skull and mandible, most probably came from the cliff exposure between Sandsfoot Castle and the old Portland Ferry Bridge. This is one of the clearer named plesiosaur records tied to the Smallmouth section. The original finder is not given in the source used here.

Colymbosaurus trochanterius (Owen, 1840)
The GCR account says most of the plesiosaur remains from Weymouth are isolated vertebrae and limb bones assigned to this species, which it describes as the best-known and most abundant Kimmeridgian plesiosauroid, reaching around 6.6 m in length. Finder not stated for the Smallmouth material.

Cimoliasaurus brevior Lydekker, 1889
Named by Lydekker in 1889 on the basis of six associated centra of immature middle cervical vertebrae from Weymouth, with type specimen BMNH 41955. The GCR account says Brown later regarded the species as a nomen dubium, so it should be treated as part of the historical literature rather than a secure modern species concept for the site.

Pliosaurus brachydeirus Owen, 1841
Represented at Smallmouth by vertebrae and teeth assigned to this pliosaur species. The GCR account lists five specimens. Original finder not stated in the source.

Pliosaurus sp.
Additional pliosaur material from the locality is listed simply as Pliosaurus sp. in the GCR account. This indicates more pliosaur material is present than can be assigned confidently to a single named species. Finder not stated.

Liopleurodon macromerus (Phillips, 1871)
The GCR account says some pliosauroid vertebrae from Weymouth were identified as this species. It is part of the historical species list for the Smallmouth fauna, though not based on a dramatic single articulated find in the source. Original finder not stated.

Ichthyosaurs

Brachypterygius extremus (Boulenger, 1904)
One of the key named Smallmouth species. Boulenger named it in 1904 from a very broad right anterior paddle. The GCR account says Boulenger did not know the locality at first, but later work showed the label clearly gave the provenance as Kimmeridge Clay of Smallmouth Sands. It also notes that Delair concluded an isolated left forelimb in Weston Museum and the type specimen BMNH R3177 belonged to the same individual.

Macropterygius thyreospondylus (Owen, 1840)
Listed in the GCR account from Smallmouth material. The same account notes that some of the old Macropterygius species were regarded by McGowan as dubious because they were based on poor material, though not necessarily impossible to define. The Smallmouth record is therefore historical but should be used with caution.

Ichthyosaurus sp.
The GCR account lists abundant ichthyosaur material under this broad heading, including vertebrae, limb bones, skull fragments and teeth. It also notes partially articulated material such as the paddle described by Boulenger and Delair, and several connected series of vertebrae. In modern times, Heather Middleton also documented an ichthyosaur skull from Smallmouth Sands, showing the site remains important for ichthyosaur finds.

Important recent pterosaur additions from the 2025 Smallmouth Sands paper

No new formal species were named in the 2025 Smallmouth Sands pterosaur paper, but the site’s diversity increased greatly
The recent paper does not erect a new named species from Smallmouth Sands. Instead, it reports a newly accessioned collection of over 500 pterosaur pieces and infers the presence of rhamphorhynchines, ctenochasmatids, dsungaripterids, darwinopterans, germanodactylids and a possible anurognathid. The collecting history given in the paper is especially useful: Heather Middleton began collecting pterosaur fossils there from 2010 onwards, Mike Harvey from 2019, and Casey Rich from 2021, with Steve Snowball also part of the main study team. In March 2025, 533 specimens were donated to the Etches Collection.

Section Architecture

This page covers the harbour-side Smallmouth Sands foreshore and adjacent low cliffs inside Portland Harbour, using the numbered embayments of recent collectors from roughly SY 669 765 to SY 672 772 as the practical field limits. It does not absorb the broader Sandsfoot Castle section farther west, and it does not force the higher mutabilis-Zone beds into a locality whose modern productive ground is mainly the lower Kimmeridge foreshore and low cliff section. The beds dip gently south-west, are low and commonly slumped, and are often masked by shingle, clay wash and harbour-side modification.

Recent Research Note

Recent work has materially improved the stratigraphic precision of Smallmouth Sands. The newly documented pterosaur collection shows that Bay 2 lies in the Pictonia baylei Biozone and Bays 3–8 in the Rasenia cymodoce Biozone, with fresh material exposed mainly from the clays above the Wyke Siltstone. That matters because the famous vertebrate yield is not a single formal “pterosaur bed”, but a practical foreshore-yield interval tied to specific lower Kimmeridge mudstones.

CORALLIAN GROUP

Sandsfoot Formation (Upper Oxfordian)

Ringstead Clay Member

Bed SM1 — Upper Ringstead Clay Member (poorly exposed contextual underlying beds)

Pale- to dark-grey variably calcareous mudstones, locally with fine calcareous laminae, pass upward into more reddish silty mudstone with siltstone lenses and the characteristic red-weathering, lens-shaped sideritic concretions of the member. In the narrow Smallmouth harbour-side section these beds are mostly contextual rather than spectacular, but they are important because they form the final Oxfordian mudstone phase beneath the condensed ironshot boundary bed. Fossils are sparse, with bivalves, echinoids and rare ammonites, and the member records quiet shelf-mud accumulation before the major omission surface at the top of the Corallian.

Osmington Mills Ironstone Member

Bed SM2 — Osmington Mills Ironstone Member / Traditional “Westbury Iron Ore Beds”

A thin pale ferruginous ooidal bed, traditionally included in the “Westbury Iron Ore Beds” of older authors but now best treated as the local Osmington Mills Ironstone Member. It is full of fossils, especially serpulids and the coarsely corrugated bivalve Ctenostreon, yet notably lacks true corals despite the older “Ringstead Coral Bed” terminology sometimes applied to it. The bed is a strongly condensed hiatal surface at the top of the Oxfordian succession and marks the last ironshot oolitic phase before the sharp incoming of basal Kimmeridge muds.

ANCHOLME GROUP

Kimmeridge Clay Formation (Lower Kimmeridgian)

Bed SM3 — Inconstans Bed (0.7 m)

Very dark grey shelly and bioturbated mudstone with ferruginous ooids and phosphatic pebbles resting sharply on the Oxfordian ironstone. The eponymous brachiopod Torquirhynchia inconstans is characteristic. This is the formal base of the Kimmeridge Clay Formation in the Dorset type area and also the Oxfordian–Kimmeridgian stage boundary. Lithologically it is an unmistakable transgressive base-bed, showing abrupt change from condensed oxic ironstone sedimentation below to darker offshore mud deposition above.

Bed SM4 — Nana Bed (0.25 m)

A thin but distinctive shell-rich bed dominated by the small oyster Nanogyra nana. It is one of the classic named lower Kimmeridge markers in the Weymouth district and lies low in the P. baylei succession. The bed is useful because it separates the basal boundary mudstone from the thicker oyster-rich and later ironstone-bearing mudstones above, while also recording one of the early shelly pulses during the first Kimmeridge marine mud accumulation.

Bed SM5 — Lower Baylei-Zone Dark Grey Mudstones With Deltoideum delta (c. 3.0 m)

Dark grey mudstones rich in the flat oyster Deltoideum delta. This is the lower, darker part of the Baylei-zone mudstone package and represents quiet, low-energy offshore shelf deposition with a benthic fauna dominated by oysters. At Smallmouth, old reptile finds from the lowest Kimmeridge were almost certainly derived in part from this broad interval and from nearby beds around it, though the modern harbour-side section rarely allows precise in-situ vertebrate logging.

Bed SM6 — Upper Baylei-Zone Pale Grey Mudstones With Thin Tabular Clay Ironstones (at least c. 6 m)

Paler, smoother grey mudstones with thin tabular clay-ironstone seams, many weathering reddish. These beds make up the thickest single exposed package in the modern Smallmouth bays and represent the upper part of the P. baylei Biozone below the Wyke Siltstone. Pictonia is recorded from beds beneath the Wyke Siltstone, and recent bay-by-bay collecting places Bay 2 within this stratigraphic interval. The unit records continued offshore mud sedimentation, but with repeated early ironstone formation and slightly greater internal differentiation than in the darker mudstones below.

Bed SM7 — Wyke Siltstone (up to c. 1.0 m; KC5)

A thin siltstone, up to about 1 m thick, packed with bivalves and locally rich enough to stand out strongly from the surrounding mudstones. It has yielded the oldest Smallmouth Rasenia horizon, including forms close to Rasenia cf. cymodoce and R. cf. triplicata, and in Dorset practice its base has long been used as the base of the Cymodoce-zone succession at KC5 level. Recent Smallmouth work is especially important here because it shows that the main modern pterosaur yield comes from the clays above this bed, making the Wyke Siltstone the key practical datum for harbour-side vertebrate collecting.

Bed SM8 — Lower Cymodoce-Zone Shales With Deltoideum delta (c. 2.0 m or more)

Dark grey shales above the Wyke Siltstone, again with Deltoideum delta present and with more Rasenia horizons recognized on the Fleet–harbour foreshore. These mudstones correspond to the lower Cymodoce-zone bays, including much of Bays 3–8 in the recent pterosaur study. They are the most important modern vertebrate-yielding beds at Smallmouth, but the fossils are generally collected loose from mud wash, pebbles and recently exposed clay rather than from a single formal in-situ bone bed. That distinction is important: this is a productive stratigraphic package, not a neatly bounded vertebrate seam.

Bed SM9 — Black Head Siltstone (0.5 m; KC8)

A second, thinner shelly siltstone 1–2 m above the Wyke Siltstone, correlating with KC8. It is a clear secondary marker in the Cymodoce-zone lower Kimmeridge and shows that brief higher-energy or shell-concentrating events continued within an otherwise mud-dominated sequence. Its importance is mainly stratigraphic, because it lets the foreshore clays above and below be fixed more securely within the lower Cymodoce succession.

Bed SM10 — Higher Cymodoce-Zone Clays Of The Southern Bays (patchy; thickness uncertain)

Beyond the Black Head Siltstone, the southernmost bays preserve only patchy higher Cymodoce-zone mudstones, usually low, slumped and shingle-masked. Nevertheless, older work recorded the youngest Smallmouth Rasenia horizon here, with microconchs referred to Rasenioides lepidula and macroconchs to Semirasenia askepta, and the recent pterosaur assemblage includes Bay 8 as its geologically youngest sampled ground. These beds are therefore real and important, but they are too intermittently exposed to support a finer honest cliff-log subdivision.

Collector Horizon Note

Most Smallmouth vertebrate material is not recovered from freshly excavated articulated skeletons in a stable cliff face. Instead it is liberated piecemeal from low cliffs and foreshore muds by slow harbour-side erosion, then picked from pebbles, clay wash and small embayments. That is why the locality produces so much isolated bone, tooth and vertebral material, and why collector-useful horizons are best described in terms of the Baylei- and Cymodoce-zone mudstone packages rather than as a mythical single “reptile bed”.

Pterosaur Assemblage Note

The recent Smallmouth pterosaur study shows that this locality is not merely a historical curiosity. The newly accessioned collection exceeds 500 pterosaur pieces, mostly three-dimensional, isolated and averaging about 14 mm in size, and the authors infer a mixed assemblage including clear rhamphorhynchines together with tentative ctenochasmatid, dsungaripteroid, darwinopteran, germanodactylid and possible anurognathid components. Because the specimens are ex situ foreshore finds, that diversity should be tied to the lower Kimmeridge harbour-side mudstones as a whole, especially the clays above the Wyke Siltstone, rather than to any one formally named bed.

Depositional Environment

The Smallmouth Sands succession records the Oxfordian–Kimmeridgian transition from condensed shallow-shelf ironshot oolite into a thicker lower Kimmeridge offshore mudstone regime. The upper Ringstead Clay represents quiet variably calcareous shelf-mud accumulation. The Osmington Mills Ironstone is a condensed ferruginous oolite formed on a major omission surface. Above it, the Inconstans and Nana beds mark the onset of lower Kimmeridge marine mud deposition, followed by Baylei-zone dark and pale mudstones with oysters and thin clay ironstones. The Wyke and Black Head siltstones represent brief shelly or slightly sandier interruptions within that mudstone regime. Recent sedimentological and collecting work suggests a generally calm marine shelf setting, probably tens to a couple of hundred metres deep, punctuated by occasional stronger storm events capable of concentrating and mixing vertebrate remains and rapidly burying them in mud-rich deposits. The harbour-side section’s modern low erosion rate is largely a product of protection by Chesil Bank and harbour sea-defence works.

Total Thickness Note

The core Smallmouth Sands harbour-side succession comprises the Oxfordian–Kimmeridgian boundary beds plus at least about 13.5 m of Baylei- and Cymodoce-zone Kimmeridge Clay above the Inconstans Bed, with only patchy Oxfordian Ringstead Clay and thin Osmington Mills Ironstone exposed beneath. Higher mutabilis-Zone clays are known in the broader Weymouth–Sandsfoot district, but they lie outside the narrow Smallmouth Sands locality defined here.

References

Jagielska, N., Middleton, H., Rich, C., Harvey, M., Snowball, S., Fitch, A. & Hone, D. Attached manuscript on the Smallmouth Sands pterosaur assemblage, treated here as recent unpublished research on the locality.
Cox, B.M. & Gallois, R.W. (1981). The stratigraphy of the Kimmeridge Clay of the Dorset type area and its correlation with some other Kimmeridgian sequences.
Cox, B.M. & Sumbler, M.G. (1994). The Oxfordian–Kimmeridgian boundary beds in southern England.
Wignall, P.B. (1990). Benthic palaeoecology of the late Jurassic Kimmeridge Clay of England.
Wright, J.K. & Cox, B.M. (2001). East Fleet–Small Mouth account in British Upper Jurassic Stratigraphy (Oxfordian to Kimmeridgian), Geological Conservation Review Series 21.
Benton, M.J. & Spencer, P.S. (1995). Smallmouth Sands account in Fossil Reptiles of Great Britain, Geological Conservation Review Series 10.
Arkell, W.J. (1947). Geology of the Country around Weymouth, Swanage, Corfe and Lulworth.
British Geological Survey Lexicon of Named Rock Units: Sandsfoot Formation, Ringstead Clay Member and Kimmeridge Clay Formation.
Snowball, S. & Middleton, H. (2023). A Field Guide to the Jurassic Fossils of the Fleet Lagoon Dorset.
Damon, R. (1884). The Geology of Weymouth, Portland and Coast of Dorsetshire.