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.

Reconstructing Wareolestes

I recently blogged about the paper I published with colleagues on a little lower jaw from the Isle of Skye, belonging to a Middle Jurassic mammaliaform called Wareolestes rex. Like many people, I believe palaeoart is a vitally important part of palaeontology, particularly as it forms a quick visual bridge between palaeontologists and the public (and other scientists!) So I'd like to share the palaeoart reconstruction I did for Wareolestes, and talk about the science behind it, and the informed speculations.

My reconstrction of Wareolestes rex. The only bit we have is the jaw, so much of the rest is informed speculation - informed by scientific evidence and living relatives. It was done in pencil and watercolour.

Mesozoic mammal art is often not especially inspiring. This is partly because, until recently, most Mesozoic mammal fossil material comprised mostly teeth, which doesn't make for exciting reconstruction. As a result, artists often choose to have their early mammals snarling to show off their teeth - the only certain part of the art! Also, there is a strange notion that small mammals are boring; but a quick google search will soon show you that they come in a huge range of sizes, shapes, colours and behaviours: inspiration for great art. However, palaeoartists have shied away from speculating about fur, whiskers, ears and eyes, erring on the side of caution and producing identikit snarling, splayed mice.

I wanted to try and do a reconstruction in an informed, but moderately speculative way. So I started work on reconstructing Wareolestes while I was still writing the paper, hoping to make informed scientific decisions based on the fossil record, and then spice it up by examining the appearance of small modern mammals.

There is a bit of a tradition among Mesozoic mammal workers of comparing our fossil beasties to the modern American opossum (Didelphis). I therefore decided to use them as the inspiration for the reconstruction. Google 'opossum', and you'll find this animal has a penchant for bearing its teeth. While I shy away from those snarling Mesozoic mammals on the whole, our Wareolestes fossil is a lower jaw with teeth, so this open-mouthed expression was fitting in this instance. Forgive me for breaking my own rules; in future reconstructions of fossils (especially those with known postcranial skeletons) I'll avoid teeth-bearing if I can help it.

The opposum Didelphis is a wonderfully charismatic creature, and often photographed bearing its teeth - handy if your fossil is a jaw with teeth and nothing else.

Our digital reconstructions (from microCT scans) were the base for drawing the mouth and teeth. As not all of the teeth were present in the Scottish fossil, I modelled the other premolars, canines, and incisors on two closely related genera: Dinnetherium and Megazostrodon. On reflection, I think the front of the snout should have been a little longer... but at this point we don't know for sure. I based the rest of the skull on Morganucodon, as Wareolestes is a morganucodontid. However, I made it more robust, because Wareolestes was larger and chunkier than it's geologically older relative.

Amazing skull and muscle reconstruction of Morganucodon by Lautenschlager et al 2016

So far, so good. But from here on, things get more speculative. We don't have much in the way of preserved fur or skin, except for a few exceptional specimens from China (but not of this genus). Undoubtedly Wareolestes and other Mesozoic mammals had fur, inherited from their non-mammal ancestors. They almost certainly had whiskers: we know this thanks to evidence in the fossil record for innervation in the snout. Whiskers probably developed in earlier non-mammalian cynodonts, which would have used them to sense their way through burrows. Therefore, whiskers are very likely to have existed in the earliest insectivorous, nocturnal mammals, being used to sense their environment and hunt for food.

I chose the shrew and the Solenodon (see below) as inspiration for the whiskers. Their whiskers extend quite far up the face, and point in multiple directions.

Beautiful shrew, showing off those sensitive whiskers. (By David Chapman, from the Cornwall Mammal Group)

The nose and ears of Mesozoic mammals, being entirely composed of soft tissue, are also impossible to reconstruct without speculation. Mesozoic mammals had well-developed olfactory bulbs, so they had a good sense of smell. I went for an opossum-like nose, simply because I liked the look of it.

This sleeping opposum's nose might be the cutest thing EVER. Will the squeeing ever stop? (I got this off pintrest, contact me if you can ID the source)

At this point in their evolution, mammals still had their post-dentary bones attached to the inside of the jaw. These bones would later reduce and detach, becoming incorporated into the middle ear. This allowed mammals to develop exquisite hearing, especially at higher frequencies. So what did they hear when the bones were still attached to the jaw? The answer is: we don't know. The postdentary bones were certainly used in hearing though. I decided a small proto-ear was fitting, based on a slightly crumpled version of a Solenodon ear. I kept them simple, small, and placed low on the head.

Close up of a Hispaniolan Solenodon (Source)

The Solenodon is a small, nocturnal insectivorous mammal found on some Caribbean Islands. It is weird on so many levels, not just because it has venomous saliva, but also as it is the only genus surviving in its family, the Solenodontidae. Phylogeneticists trace their origins back to the Cretaceous, making this an altogether unique animal and a good analogue to find inspiration for the life appearance of Mesozoic mammals. Because of this, I chose the dark back and upper face of the Solenodon as inspiration for the colour pattern on Wareolestes. However, I then decided to add a little cheek and eye patterning.

Finally, the eyes. It's hard to say how large the eye would have been relative to the head. I decided to go for something I know and love: the eye of a rat. This is a total bias on my part, because as a many-time rat-owner, I was always delighted by those dark chocolate beady eyes greeting me each morning, staring with demented twitchiness and tiny black pupils pointing in opposite directions. Mental. However it does leave me open to all the "aren't Mesozoic mammals just a bunch of rats anyway?" comments people just can't restrain themselves from making... sigh*.

So there you have it. This was my process in creating a Wareolestes rex reconstruction. I played it kind of safe - I could have speculated about the rest of the body, but decided it was a step too far. This is my first proper go at palaeoart, so theres still a lot to learn. Hopefully in the coming field seasons we'll find more of the skeleton and I'll be able to revise the image based on more evidence. In the meantime, I'd love to hear you opinions, ideas, and comments - get in touch on twitter: @gsciencelady

*Wareolestes is of course not a rodent, as rodents didn't evolve for another 100 million years. The resemblence is superficial, anatomically they are totally different.


References
 
Benoit J., Manger P. and Rubidge BS. 2016 Palaeoneurological clues to the evolution of defining mammalian soft tissue traits. Scientific Reports.

Lautenschlager S., Gill P, Luo Z-X., Fagan MJ., and Rayfield EJ. 2016 Morphological evolution of the mammalian jaw adductor complex. Biological Reviews.

Panciroli E., Benson RBJ., and Walsh S. 2017 The dentary of Wareolestes rex (Megazostrodontidae): a new specimen from Scotland and implications for morganucodontan tooth replacement. doi: 10.1002/spp2.1079