Rosa Rubicondior: Creationism In Crisis - A 145-Million-Year-Old Fossil Early Mammal From Dorset, England

(L-R) Dr Roy Smith and University of Portsmouth student Ben Weston by the flint bed in Durlston Bay near Swanage, which is the layer of rock which the mammal fossil came out of.

Credit: Ben Weston.

New species of tiny Cretaceous mammal discovered by University of Portsmouth student | University of Portsmouth

When someone grows up being threatened with divine punishment for merely entertaining doubts about the literal truth of the Bible, it's hardly surprising that real-world evidence struggles to break through the psychological defences they've built to protect themselves. This phenomenon is what atheist author and philosopher, Professor Peter Boghossian refers to as doxastic closure — a mental state in which contrary ideas are shut out before they can even be considered.

Former young-Earth creationist and now science advocate and geologist Glenn Morton once described it as like having a “gatekeeper demon” perched on the edge of your consciousness—filtering out any facts or logical arguments that challenge creationist beliefs, while admitting only those misrepresentations of science that appear to support them.

In this mindset, inconvenient realities — such as the discovery of a 145-million-year-old fossil of an early mammal — are unlikely to dent the conviction that the Earth is only 6,000 to 10,000 years old, and that all animals were created in a single supernatural event. In this view, evolution is simply an illusion, no matter how well the evidence supports it.

Even so, for any creationist with the courage and intellectual honesty to read this far, the story of that inconvenient little fossil is well worth exploring. It was discovered by a palaeontology student from the University of Portsmouth, along the Dorset coast of England, and is the subject of a recent paper in Proceedings of the Geologists’ Association.

This find marks the first discovery of a multituberculate jaw at Swanage since Victorian times. Its distinct size and shape confirmed it as a completely new species.

Tell me all about the multituberculate, please. Certainly. Here's a comprehensive overview of multituberculates, a remarkable and long-lived group of extinct mammals:

Multituberculates: The “Rodents” of the Mesozoic

Overview

Multituberculates were an extinct order of small to medium-sized mammals (Order Multituberculata) that lived from the Late Jurassic (~160 million years ago) through to the Early Oligocene (~35 million years ago) — a stunning evolutionary success spanning over 120 million years. They are among the longest-lived mammalian groups in Earth’s history.

They were so successful that they are often dubbed the “rodents of the Mesozoic,” not because they are ancestral to rodents (they're not), but because they filled a similar ecological niche—gnawing herbivores and omnivores.

Name and Dentition

The name Multituberculata comes from the multiple rows of cusps ("tubercles") on their cheek teeth, which were highly specialised for chewing plant matter.

Incisors: Like modern rodents, multituberculates had large, chisel-like incisors at the front of the jaw. These were used for gnawing.
Diastema: A toothless gap behind the incisors allowed space for manipulating food.
Cheek Teeth: Their molars had multiple rows of cusps, ideal for grinding tough plant material. The arrangement of cusps often looks like a tiny washboard under the microscope.

Size and Appearance

Most multituberculates were mouse- to rat-sized, though some species, such as Taeniolabis, were beaver-sized and likely among the largest mammals before the extinction of the dinosaurs.
They likely had fur, whiskers, and claws. Their skeletons suggest burrowing or climbing habits depending on the species.

Ecology and Behaviour

Multituberculates were mostly herbivorous or omnivorous, consuming seeds, nuts, fruits, and possibly insects.

Some species, like Ptilodus, had prehensile tails and grasping limbs, suggesting an arboreal (tree-dwelling) lifestyle.
Others were terrestrial burrowers, somewhat like modern moles or gophers.

Evolutionary Position

Multituberculates are not direct ancestors of modern mammals, but they belong to the wider clade of mammals. They likely branched off early in mammalian evolution, before the divergence of modern therians (marsupials and placentals).

Their evolutionary relationships are still debated, but recent analyses often place them within or close to Allotheria, a separate mammalian subclass distinct from therians.

Extinction

Multituberculates persisted even after the Cretaceous-Palaeogene (K-Pg) extinction that wiped out the non-avian dinosaurs. However, they finally disappeared in the Early Oligocene (~35 million years ago).

Their extinction may have been due to:

Competition with newly emerging rodents and placental mammals, which had more efficient jaw mechanics.
Changing climates and habitats, particularly the spread of open grasslands.

Fossil Distribution

Multituberculate fossils have been found in:

North America
Europe
Asia
Some from Africa and South America, though rarer.

Notably, the recent find in Swanage, Dorset, UK, is the first multituberculate jaw from that location since Victorian times. The fossil likely dates to the Early Cretaceous (~145 million years ago) and represents a new species.

Significance

Multituberculates are crucial for understanding early mammal evolution.
They show how mammals could thrive even under the shadow of dinosaurs.
Their extinction helped clear the ecological path for rodents, which then underwent their own adaptive radiation.

A detailed account of the discovery is also available in a University of Portsmouth news release.

New species of tiny Cretaceous mammal discovered by University of Portsmouth student
A Portsmouth palaeontology student's fieldwork discovery reveals a 145-million-year-old prehistoric mammal from the Dorset coast

It marks the first multituberculate jaw found at Swanage since Victorian times
Third new species discovered in Dorset by University of Portsmouth undergraduate students in under a decade
Portsmouth team carried out “digital dental surgery” using CT scanning to isolate individual teeth for detailed study

A University of Portsmouth student has discovered a new species of prehistoric mammal dating back 145 million years to the Berriasian age, providing fresh insights into the diversity of early mammals that lived alongside dinosaurs.

Benjamin Weston, an undergraduate palaeontology student, made the remarkable discovery while conducting fieldwork in the cliffs of Durlston Bay near Swanage, Dorset. The fossilised lower jaw he found represents a completely new species of multituberculate - an extinct group of early mammals known for the distinctive tubercles on their posterior teeth.

The 16.5mm-long jaw is characterised by a long pointed incisor at the front, followed by a gap and then four razor-sharp premolars. While superficially resembling a rabbit's jaw, the pointed incisors and distinctive premolars identify it as belonging to the multituberculate group.

This discovery, published in Proceedings of the Geologists' Association, marks the first multituberculate jaw found at Swanage since Victorian times, and its unique size and shape confirmed it as an entirely new species.

I instantly had my suspicions of what the jaw was when I found it at the beach, but couldn’t have imagined where the discovery would take me. I’m extremely grateful to the team and to the university for helping me take my first steps into academic palaeontology.

Benjamin T. Weston, first author.
School of the Environment and Life Sciences
University of Portsmouth, Portsmouth UK.

Dr Roy Smith and Emeritus Professor David Martill, who supervised the research, enlisted the expertise of Dr Steve Sweetman, a former Portsmouth student and now honorary research fellow, who specialises in rare Early Cretaceous mammal fossils from the Isle of Wight and Isle of Purbeck regions.

This was not the first time a student made a once-in-a-lifetime discovery in Dorset. In 2017, undergraduate Grant Smith recovered fossils of two new species of Humankind's earliest ancestors from rocks exposed in cliffs near Swanage.

This is a remarkable find that reminds me of when Grant found those extraordinary eutherian mammal teeth. When I first saw Grant's specimens, my jaw dropped - and I had exactly the same reaction to Ben's multituberculate jaw. It's incredible that Durlston Bay keeps delivering such significant mammal discoveries by our undergraduate students.

Dr Steven C. Sweetman, co-author
School of the Environment and Life Sciences
University of Portsmouth, Portsmouth UK.

Advanced technology reveals hidden details

The delicate fossil presented challenges, with pieces of rock obscuring vital details. The University's advanced CT scanning capabilities proved crucial to the research. Dr Charles Wood, Senior Scientific Officer in the School of Electrical and Mechanical Engineering, used CT scanning to reveal the specimen inside the rock, producing remarkable results due to the contrast between fossil and rock.

The team then collaborated with Jake Keane, a former Portsmouth palaeontology student now working in Abu Dhabi (UAE), who processed the CT scans digitally. Within hours, Keane had digitally removed all surrounding rock and performed “digital dental surgery” to isolate individual teeth for detailed study.

Using these digital files, Lead Technician John Fearnly at the University's 3D printing lab in the Faculty of Technology created replicas magnified ten times, allowing safe study of the precious fossil without risk of damage.

Introducing Novaculadon mirabilis

The new species has been named Novaculadon mirabilis, with “novacula” describing its razor-like back teeth and “mirabilis” referring to the miraculous preservation of the specimen.

Portsmouth palaeontology student Hamzah Imran created an artistic reconstruction showing the animal as a small, furry creature with speculative spots and stripes.

The fossil evidence suggests Novaculadon mirabilis was omnivorous, likely feeding on small invertebrates such as worms and insects. The sharp-pointed incisors and ridged, blade-like premolars indicate a feeding strategy distinct from modern rodents like squirrels and rats.

Looking back now that the discovery has been published, I am amazed at how many people it took to describe this little mammal. I especially appreciated that all team members were University staff or present and former students - a true team effort including academics, technicians, alumni, and students with diverse talents across three departments.

Emeritus Professor David W. Martill, co-author
School of the Environment and Life Sciences
University of Portsmouth, Portsmouth UK.

The research demonstrates how early mammals carved out ecological niches while dinosaurs dominated the landscape. Although multituberculates survived the extinction event that killed the dinosaurs, they eventually became extinct around 33 million years ago during the Oligocene period.

Multituberculata represents the most diverse order of Mesozoic mammals, with over 200 known species ranging from mouse-sized to beaver-sized. These mammals occupied various ecological niches over their 130-million-year evolutionary history, from burrow-dwelling to squirrel-like tree climbers.

The discovery adds to Portsmouth's growing reputation in palaeontological research and demonstrates the value of undergraduate fieldwork in advancing scientific knowledge.

Publication:
Weston, Benjamin T.; Sweetman, Steven C.; Kean, Jake; Wood, Charles; Martill, David M.; Smith, Roy E.
A new multituberculate (Mammalia, Allotheria) from the Lulworth Formation (Cretaceous, Berriasian) of Dorset, England
Proceedings of the Geologists' Association (2025) 101128, DOI: 10.1016/j.pgeola.2025.101128

Abstract
A new genus and species of plagiaulacid multituberculate (Mammalia, Allotheria, Multituberculata) is described from the Cherty Freshwater Beds, Warbarrow Tout Member of the Lower Cretaceous Lulworth Formation of the Purbeck Group, Dorset, United Kingdom. The new taxon is represented by a complete, well preserved left dentary containing the incisor, p2–4, with alveoli for m1–2. This new specimen is the most complete multituberculate material yet recovered from the Purbeck Group. It is also the first mammal to be recovered from the so-called ‘Flint Bed’ (DB97).

1. Introduction
Multituberculates are the most diverse group of Mesozoic mammals: a highly successful clade that existed from the Middle Jurassic throughout the Mesozoic and persisted past the Cretaceous/Paleogene (K/Pg) boundary, surviving until the early Oligocene (Ostrander, 1984; Kielan–Jaworowska et al., 2004). They possessed large incisors, a conspicuous diastema between the lower incisor and premolar series, multiple, typically commensurate cusps on the premolars and molars, and an enlarged, blade-like fourth lower premolar (Kielan–Jaworowska et al., 2004). The first multituberculate to be named, Plagiaulax becklesii Falconer, 1857 (Owen, 1871), is from the Berriasian part of the late Upper Jurassic to early Lower Cretaceous Purbeck Group of Durlston Bay, Dorset, southern England. Subsequently, eight additional multituberculate taxa have been described from the Purbeck Group (Kielan–Jaworowska et al., 2004, and references therein). Here we describe a new genus and species of plagiaulacid multituberculate from the Lulworth Formation of the Purbeck Group (Warbarrow Tout Member, Cherty Freshwater Beds) of Durlston Bay, Dorset (Fig. 1).

Fig. 1. A, outline geological map of Durlston Bay and the southern part of Swanage Bay, east Dorset, United Kingdom. Star denotes the collection locality. B, map showing the location of Durlston Bay in the southeast of the United Kingdom.
Adapted from Sweetman et al. (2017).

1.1. Historical note
In 1854 the Rev. P. B. Brodie and Mr C. Wilcox sent their combined collection of small vertebrate remains from the Purbeck Group of Durlston Bay to Richard Owen at the British Museum, London. This collection included mammal remains collected by the former from what was later to be known as the ‘Mammal Bed’ (Fig. 2, bed DB 83 of Clements, 1993). This was, until the latter part of the 20th Century, one of very few horizons worldwide to yield Mesozoic mammal remains. Two of Brodie's specimens, both tooth-bearing left mandibular rami, were sufficient for Owen to describe and name the spalacotheriid Spalacotherium tricuspidens Owen, 1854. Brodie continued to collect mammals from this horizon during the years 1855–1856 and also sent these to Owen. However, before they were received, and based on material in Brodie's original collection, Hugh Falconer named two further Purbeck mammals, Plagiaulax becklesii (sic) and P. minor Falconer, 1857, the first multituberculates to be described and named.

Fig. 2. Composite stratigraphic log of part of the Lulworth Formation of the Purbeck Group exposed in the central part of Durlston Bay showing horizons marked with a silhouette where mammals have been recovered. Bed 97 where NHMUK PV M 119716 was found is indicated by a red silhouette. Redrawn from Clements (1993) using the author's “erosional profile” but with some additional bed names. Detailed comments on lithologies and palaeontology are provided by Clements (1993) in which all bed numbers bear the prefix DB.

In 1856, at Owen's invitation, Samuel H. Beckles, a well-known south of England fossil collector, commenced a major excavation at the site yielding the spalacotheriid and multituberculate specimens. The scale of the quarrying operation was remarkable, and it probably represents one of the largest palaeontological excavations ever undertaken in the UK. According to a contemporary report (Kingsley, 1857.1) Beckles removed 15.85 m² of overburden to expose approximately 650 m2 of the ‘Mammal Bed’. This resulted in the recovery of many new mammal specimens permitting Owen to describe the triconodontid Triconodon mordax Owen, 1859, the dryolestid Stylodon pusillus Owen, 1866 (later to be placed in his genus Amblotherium as A. pusillum), and a number of others. These include the multituberculates Bolodon crassidens and B. falconeri, amongst sixteen species described by Owen (1871).

However, for reasons that are unclear, Beckles ceased work some nine months after commencing and following cessation of quarrying activities very few mammal specimens were reported from this horizon. It was not until 1986 that significant new Purbeck Group mammals were recovered during a study by Paul Ensom. Ensom discovered microvertebrate-rich sediments at Sunnydown Farm Quarry (NGR SY 9822 7880), located some 5 km to the west of Durlston Bay (Ensom et al., 1994; Ensom, 2000). Ensom went on to process samples from this locality and a number of other horizons and localities using wet screening techniques and succeeded in recovering more than 800 mammal specimens, mostly isolated teeth. The most productive locality was the first discovered at Sunnydown Farm where two microvertebrate-rich horizons were exposed, both in the Cherty Freshwater Beds (Fig. 2), the most productive of which correlates with DB 102 of Clements (1993) (Fig. 2). At least sixteen mammal species have been recorded from this locality including the multituberculates Albionbaatar denisae Kielan-Jaworowska and Ensom, 1994.1, Gerhardodon purbeckensis Kielan-Jaworowska and Ensom, 1992 and Sunnyodon notleyi Kielan-Jaworowska and Ensom, 1992, now with emended species name, S. notleyorum (Martin et al., 2021), which do not occur in the ‘Mammal Bed’ assemblage.

Until the description of new microvertebrate sites (e.g., Ensom et al., 1994; Ensom, 2000) almost all Mesozoic mammal specimens from the Purbeck Group of Dorset were obtained during the course of Beckles' 1850 excavations. However, in 1969 a specimen representing a new species of ‘symmetrodont’ mammal was found during the course of an undergraduate field trip to Durlston Bay. This was obtained from a horizon approximately 4 m above the Mammal Bed, and just to the south of the original pit. It is now known to represent a new species of the spalacotheriid Spalacotherium, S. hookei Gill, 2004.1, first described by Owen (1854). Subsequent to that, and also during the course of undergraduate field work, two other highly significant mammal specimens have been obtained from Durlston Bay, both from a beach-level exposure of the Mammal Bed some distance to the north of Beckles' pit. These are the eutherians Durlstotherium newmani Sweetman et al., 2017 and Durlstodon ensomi Sweetman et al., 2017.

Fig. 3. Holotype left dentary of Novaculadon mirabilis gen. et sp. nov. NHMUK PV M 119716 from the Lulworth Formation, Purbeck Group at Durlston Bay. In: A, buccal view; and B, lingual view. Scale bar represents 5 mm.

Fig. 4. Images of 3D model generated from XCT scans of the holotype left dentary of Novaculadon mirabilis gen. et sp. nov. NHMUK PV M 119716 from the Lulworth Formation, Purbeck Group at Durlston Bay. In: A, buccal view; B, lingual view; C, occlusal view; D, ventral view; E, anterior view; and F, posterior view. Scale bar represents 5 mm.

Weston, Benjamin T.; Sweetman, Steven C.; Kean, Jake; Wood, Charles; Martill, David M.; Smith, Roy E.
A new multituberculate (Mammalia, Allotheria) from the Lulworth Formation (Cretaceous, Berriasian) of Dorset, England
Proceedings of the Geologists' Association (2025) 101128, DOI: 10.1016/j.pgeola.2025.101128

Copyright: © 2025 The authors.
Published by Elsevier B.V. Open access.
Reprinted under a Creative Commons Attribution 4.0 International license (CC BY 4.0)

The discovery of a new species of multituberculate mammal from the Early Cretaceous of Swanage presents a serious challenge to young-Earth creationism. According to creationist doctrine, mammals were created alongside all other animals just a few thousand years ago, with no evolutionary history and no deep fossil record. Yet here is a tiny jawbone, entombed in rock that has been radiometrically and stratigraphically dated to approximately 145 million years ago — long before any human ever walked the Earth. For this to be dismissed or ignored, as creationists are often forced to do, demands a wilful rejection of multiple, independent lines of evidence.

Even more problematic for creationist claims is the anatomical detail of the fossil itself. This is not a modern mammal inexplicably buried in “ancient” rock—it is a clearly transitional form, with characteristics typical of multituberculates: specialised gnawing incisors, complex cheek teeth, and traits placing it firmly within a long-extinct branch of the mammalian tree. It fits precisely where evolutionary theory predicts it should, in both time and morphology. There is no reason for such a creature to exist in a “created kind” model, nor any logical justification for why it would be found in rocks predating the supposed biblical Flood by over 100 million years.

If one were to take the creationist model seriously, one would have to accept that a global deluge somehow sorted this exquisitely preserved jawbone into precisely the right geological stratum alongside the expected fossil fauna and flora of its time — an implausible feat of hydraulic sorting that strains credibility. More plausibly, and far more simply, this fossil reflects what the evidence has shown again and again: mammals were already diversifying during the time of the dinosaurs, not spontaneously created in their modern forms. Finds like this one don’t just contradict creationism — they make a mockery of it.

Advertisement

Amazon