Scotland's First Jurassic Mammal - our paper is out!

The first mammal fossil ever found from the ‘time of dinosaurs’ was announced almost 200 years ago*. It was a small jaw just a couple of centimetres across, which emerged from Middle Jurassic rocks in Oxfordshire, England. It was 150 years later that the first such beast was found in Scotland. This week my colleagues and I described that Scottish specimen in detail for the first time, along with stunning new material from the same species.

The most complete Mesozoic-aged mammal jaw found in Scotland so far, belonging to Borealestes serendipitus, a small insectivorous animal.

The animal these fossil bones belong to is delightfully called Borealestes serendipitus, the ‘northern rogue, found by chance’. But it was not just luck, its founder Dr Michael Waldman tells me. Mike was leading a group of school pupils on an outdoor skills trip to the Isle of Skye in the 1970s, and he knew from his research that there were fossils in the area. He never imagined they would be so spectacular or rare of course. Upon finding the first jaw, Mike brought the tiny fossil, no bigger than a thumbnail, to his mentor and friend, Professor Robert ‘Bob’ Savage at the University of Bristol. Together they returned to Skye find more fossils from Scotland’s Jurassic heyday.

Since the first publication on Borealestes in 1972, very little work has been done on it. Several jaws, a partial skeleton, and some isolated teeth were found, but only two partial jaws were published, and the descriptions were sparse. This new paper in the Journal of Vertebrate Paleontology is part of my ongoing research on the mammals of Jurassic Scotland, begun while I was at National Museums Scotland (NMS) and the University of Edinburgh. I’m part of a team from NMS and the Universities of Oxford and Birmingham who have been working on the Isle of Skye since 2010, and finding yet more of this animal and the many creatures that lived alongside it.

A new fossil jaw I found in 2016. Only the tooth tips were protruding from the rock.

Our paper is first and foremost anatomical, clarifying the identification (diagnosis) of Borealestes. In other words, how do you recognise Borealestes if you find it? This is predominantly based on the shape of the teeth. In 2003 a close relative, Borealestes mussettae, was named from isolated teeth from the English Jurassic-aged site of Kirtlington. Our new paper sets out the differences between the two species, and re-evaluates all previously known specimens in light of this new information (some were previously misidentified). 

The fossil specimens are quite exceptional. They include the most complete Mesozoic mammal jaw found so far in Scotland: a very long and slender dentary with delicate jaw hinge and perfect insect-munching teeth. There is also a Borealestes specimen I found myself during fieldwork and so feel a personal connection to, as well as the upper tooth row of a partial skeleton that I’m currently completing work on with my colleagues (watch this space!) 

The micro CT-scan of the jaw I found in 2016 revealed the rest of the bone hiding below the surface. Without computed tomography (CT) it is unlikely we could have studied this fossil intact.

This publication is the next in a series of papers on Borealestes. In 2018 my colleagues and I described the ear bones of this Jurassic animal, whereas this paper focuses on the jaw and dentition. With five jaws figured in this publication, all from micro CT-scans, the upper molar row and incisors known for the first time, and countless individual teeth re-evaluated, this paper expands our understanding of this modest docodontan, and adds significantly to the number of Mesozoic mammal specimens known from Scotland. 

*The jaw belonged to Phascolotherium. Other mammal jaws were found previous to this one, but it was the first one recognised for its significance, and was announced (alongside Megalosaurus) during the inaugural address of the Geological Society of London by its first President, William Buckland, in 1824.

References

Panciroli, E, Benson, R, and Luo, Z-X. 2019. The mandible and dentition of Borealestes serendipitus (Docodonta) from the Middle Jurassic of Skye, Scotland. Journal of Vertebrate Paleontology. https://doi.org/10.1080/02724634.2019.1621884

International Women's Day: Frances Mussett

I was recently asked by a reviewer to amend the name of one of the animals my colleagues and I were re-describing, Borealestes mussetti. ‘It should be B. mussettae’ the reviewer explained, ‘as it honours Frances Mussett’. I’d encountered Mussett’s name many times in my research, but through my own subconscious gender bias, had assumed Mussett was a man. It turns out that the original description of Borealestes mussetti used the wrong gender when erecting this species, and so Frances Mussett became masculinised both through taxonomy and assumption. 

This is one of the subtler ways in which women can be written out of science, and out of history. With International Women’s Day, 8^th March, on our doorstep yet again (and Women and Girls in Science Day just passed, 11^th February) it feels right not only to amend her namesake species (paper coming soon!), but to share some of the achievements of Mussett’s scientific career, and her role in early mammal palaeontology.

Despite being on so many of the most significant papers on Mesozoic mammals, Frances Mussett is poorly biographed. She is frequently mentioned as the assistant of Kenneth Kermack (1919-2000), one of the big names in Mesozoic mammal palaeontology, but seldom as a researcher in her own right. Mussett was a work colleague and friend of the Kermacks (a married couple and both significant palaeontologists), as well as carrying out field work with them. Her publications included co-authorship of papers on two of the most important early mammaliaforms, Kuehneotherium and Morganucodon, and although she didn’t hold a PhD she was undoubtedly a capable researcher and meticulous writer.

Reconstruction of Morganucodon by Bob Nicholls

After her bachelors degree at Birkbeck, Universoty of London, Mussett joined the thriving team of palaeontologists at University College London (UCL), collecting fossils and publishing in the 1950s-70s. The team included Professor Kenneth Kermack, Dr Doris Kermack, Jackie Papworth, Patricia Ferguson (née Lees) and Mussett, the latter two women employed by the department as Kenneth Kermack’s research technician and assistant, respectively. While Ferguson and Mussett’s roles overlapped, Mussett was more heavily involved in manuscript preparation, as well as some teaching. Mussett suffered from diabetes, and had to be strict in order to manage the condition. Restrictions at the time mean that due to her diabetes Musset was not allowed to drive, and so Lees did any driving necessary during fieldwork. 

In the 1960s the UCL team worked regularly at the Welsh fissure fills – a series of cracks in Carboniferous rocks that are filled with sediment from the Late Triassic to Early Jurassic. This sediment has proven rich in fossil material, and Kermack, Kermack and Mussett named a new genus of one of the very earliest mammaliaforms, Kuehneotherium, from among these finds (1968). 

Kermack, Mussett and Rigney (1973) were the first to realise that the Late Triassic and Early Jurassic mammals with triconodont teeth (where the main cusps are arranged in a line along the tooth axis) were a separate group from mammals with the same tooth arrangement that lived later, in the Middle Jurassic to Early Cretaceous. These were once collectively known as ‘Triconodonta’ (Osborne, 1888), but the team divided them into sub-groups, calling their earlier ones Morganucodonta, and the later ones Eutriconodonta. This was an important shift in our understanding of early mammal relationships, and later it was realised the two suborders were completely distinct (Kielan-Jaworowska et al., 2004).

One of the most famous and pivotal early mammals is Morganucodon. It belongs right at the base of the mammaliaform tree, is well-known in terms of fossil material. Along with Kuehneotherium and Sinoconodon, this genus is a touchstone for Mesozoic mammal palaeontologists. Mussett co-authored two major monographs on Morganucodon’s skull and jaw with Kenneth Kermack (1973,1981). Professor Kielan-Jaworowska, one of the most important Mesozoic mammal palaeontologists of all time, said ‘in addition to this wonderful skull, Kenneth and Frances had at their disposal thousands of isolated bones of Morganucodon watsoni from the fissure fillings in Wales’ (Kielan-Jaworowska, 2013: p80). 

The research Mussett was involved in through her role at UCL spanned much of the synapsid family tree, including examining the jaw articulation of docodonts, erecting the name Eupantotheria (Kermack and Mussett, 1958), and looking at the ears of Permian synapsids (Kermack and Mussett, 1983). In the 1970s the UCL team began work at Kirtlington Cement Quarry, a Middle Jurassic locality in England rich in small vertebrate fossils. This led to publications on the mammals from this site (Kermack, Lee Lees, Musset, 1987), as well as lissamphibians (Evans, Milner and Mussett, 1988, 1990). As an important member of the team, Mussett was part of the fieldwork, as well fullfilling her vital role assisting in manuscript preparation and editing.

After the Kermacks retired, Frances Mussett stayed on at UCL, carrying on teaching and other work, but she never published independently. Upon retirement, she donated many specimens to UCL as well as the Natural History Museum in London. Collected between 1961 and 1994 and unusually well-documented (even including the day of collection in some cases), these finds included material from the Isle of Wight, such as the bones of marine reptiles. There were also specimens of Morganucodon, Kuehneotherium and the many other exceptional mammals and small vertebrates collected during her career working alongside the Kermacks (many of these are part of the Kermack Collection). In 2003, Mussett was acknowledged in the naming of Borealestes mussetti, to recognise the ‘major participation of Dr [sic] Frances Mussett in the accumulation of the Kirtlington fauna’ (Sigogneau-Russell, 2003). 

The holotype lower molar tooth of Borealestes mussettae.

And so we come full circle. Here I am sitting in the Oxford Natural History Museum with specimens of B. mussettae – now emended to the feminine form – glinting up at me from under the lights of the microscope. Mussett herself must have spent uncountable hours this way, gazing down the eyepiece at tiny perfections of anatomy from the dawn of mammals. I wonder if she ever saw her namesake species? Undoubtedly the many hours she and women like her have spent contributing to science deserves recognition, not just on International Women’s Day, but every day.

(Note: this blog was emended as previously Pat Lees and Patricia Ferguson were listed as seperate lab members, but they were one and the same: Patricia 'Pat' Lees married John Ferguson, a senior technician at UCL and took his surname. The university Mussett attended was aldo added, and the information about her diabetes. 10/3/19 Thanks to Pam Gill for this extra information.)

References

Evans SE, Milner AR and Mussett F. 1988. The earliest known salamanders (Amphibia, Caudata): a record from the Middle Jurassic of England. Geobios, 21: 539-552.

Evans S.E, Milner AR and Mussett F. 1990. A discoglossidfrog from the Middle Jurassic of England. Palaeontology, 33: 299-311.

Gabriel N. 2018. Specimen of the Week 337: The Mussett Collection.

Kielan-Jaworowska Z, Cifelli RL and Luo Z-X. 2004. Mammals from the age of dinosaurs: origins, evolution, and structure. Columbia University Press.

Kielan-Jaworowska Z. 2013. In pursuit of early mammals. Indiana University Press.

Kermack KA and Mussett F. 1958. The jaw articulation of the Docodonta and the classification of Mesozoic mammals. Proceedings of the Royal Society of London. Series B-Biological Sciences, 149(935), pp.204-215.

Kermack DM, Kermack KA and Mussett F. 1968. The Welsh pantothere Kuehneotherium praecursoris. Journal of the Linnean Society of London Zoology, 47: 407–423.

Kermack KA, Mussett F and Rigney HW. 1973. The lower jaw of Morganucodon. Zoological Journal of the Linnean Society, 53: 87–175.

Kermack KA, Mussett F and Rigney HW. 1981. The skull of Morganucodon. Zoological Journal of the Linnean Society, 71: 1–158.

Kermack KA and Mussett F. 1983. The ear in mammal-likereptiles and early mammals. Acta Palaeontologica Polonica, 28.

Sigogneau-Russell D. 2003. Docodonts of the British Mesozoic. Acta Palaeontologica Polonica, 43: 357-374.