David M.S. Watson, palaeontologist, was the son of David Watson and his wife, Mary Louise Seares. He graduated at the University of Manchester in 1907 with a first in geology. While still an undergraduate he was co-author of a major paper on the fossil plants of the Upper Carboniferous. From 1909 he was a demonstrator and from 1912 lecturer in vertebrate palaeontology at the University of Manchester, until 1921. One of his main interests was in early fishes, another in the mammal-like reptiles and the origin of mammals. In 1911 he published a paper on Diademodon fossils from the Upper Triassic strata of the Karoo in the Annals and Magazine of Natural History. That same year he visited South Africa and made a large collection of Karoo fossils. During a visit to the Albany Museum he studied the well-preserved fossil remains of an amonodont mammal-like reptile, found at Conway in the Karoo and presented to the museum by N. and D. Collet. He published the results in an important paper, "The skeleton of Lystrosaurus" (Records of the Albany Museum, 1912, Vol. 2(4), pp. 287-295). In the same volume (pp. 296-299) he described two new species from remains collected at Cradock which he found in the museum's fossil collection. One appeared to be the earliest known procrocodilian, the other a primitive amphibian then only known from the Permian of Europe.
During the next two years he published eight more papers on his findings in South Africa. Two of these appeared in the Annals and Magazine of Natural History (1913) and dealt with "Some features of the structure of the Theracephalian skull" and "Further notes on the skull, brain, and organs of special sense of Diademodon". The other six, in the Geological Magazine (1913-1914), described "A new cynodont from the Stormberg", "The limbs of Lystrosaurus", "Micropholis stowi, Huxley, a temnospondylus amphibian from South Africa", "The Beaufort beds of the Karroo System of South Africa", "The larger coal measure amphibia", and "The zones of the Beaufort beds, South Africa". In the latter paper he established biostratigraphical zones in the Beaufort Group. At this time it was generally believed that the cynodonts were the precursors of the mammals. However, in the above publications Watson tended to derive both the mammals and cynodonts from therocephalians or pre-therocephalians and suspected parallel development of the various orders of therapsids towards mammals. Years later he introduced, among others, the genus Anteosaurus of therapsids - a carnivorous animal from the lowermost strata of the Beaufort Group based on a skull in the British Natural History Museum - in "The bases of classification of the Theriodontia" (Proceedings of the Zoological Society of London, 1921). Later papers relating to southern Africa included "On the skeleton of a Bauriamorph reptile" (Ibid, 1931), which dealt with various species of therocephalians, "Dicynodon and its allies" (Ibid, 1948), and "A classification of therapsid reptiles" (with A.S. Romer; Bulletin of the Museum of Comparative Zoology, Harvard College, 1956).
Watson visited Australia in 1914 and subsequently described the embryology of the skull of the duck-billed platypus. On his return from Australia he collected fossils in the Lower Triassic red beds of Texas. From 1911 he had been an honorary lecturer in vertebrate palaeontology at University College, London, and in 1921 was appointed there as professor of zoology and comparative anatomy, a position he held until his retirement in 1951. He gained a reputation as a superb teacher. After his retirement he was a visiting professor at Harvard University (1952-1953) and thereafter worked in the Zoology Department of University College until 1965. He wrote many significant papers on mammalian and reptile origins, early fishes, and the evolution of amphibians. Most of these were published in the Philosophical Transactions of the Royal Society of London from 1908 to 1954. He also wrote a book on Palaeontology and modern biology (1951, 216p).
During World War I, from 1916 to 1918, he was a lieutenant in the Royal Naval Volunteer Reserve. Subsequently he was a member of the Agricultural Research Council (1931-1942) and one of the trustees of the British Museum (1946-1963). In addition to his achievements in palaeontology he had a deep knowledge of Chinese archaeology. He was elected a Fellow of the Royal Society of London in 1922 and was awarded medals by the Geological Society of London (1935), the United States National Academy of Sciences (1941), the Royal Society of London (1942), and the Linnean Society (1949). The University of Cape Town awarded him an honorary Doctor of Science (DSc) degree in 1929, the University of Aberdeen an honorary Doctor of Laws (LLD) degree in 1943, and the University of the Witwatersrand an honorary DSc in 1949. He was married to Katherine Parker, with whom he had two daughters.
Watson visited South Africa again in 1929 to attend the annual meeting of the British Association for the Advancement of Science. At that meeting he was president of Section D of the British Association and his presidential address was titled "Adaptation".