So far, the Palaeozoic fossil jawless vertebrates have not provided any direct evidence for the organization of the gills, apart from vague impressions--supposedly left by gill filaments--on the bony surface of the gill chamber in certain armoured forms or 'ostracoderms' (for example, osteostracans and heterostracans). The latter are currently regarded as more closely related to the living jawed vertebrates (crown gnathostomes) than to the living jawless vertebrates (hagfish and lampreys, or cyclostomes). Here we report the first direct evidence for the position of the gill filaments--possibly supported by gill rays--enclosed by gill pouches in a 370-million year (Myr)-old jawless vertebrate, Endeiolepis, from the Late Devonian fossil fish site of Miguasha, Quebec, Canada. This extinct jawless fish has much the same gill organization as living lampreys, although it possesses an unusually large number of gill pouches--a condition unlike that in any extant vertebrates and that raises questions about gill development. Endeiolepis is currently regarded as a close relative of anaspids, a group of 410-430-Myr-old 'ostracoderms'. Assuming that current vertebrate phylogeny is correct, this discovery demonstrates that pouches enclosing the gills are primitive for vertebrates, but have been subsequently lost in jawed vertebrates.
THE history of the case which came under my own observation is as follows : -S.W., set. 42, a very stout woman, and the mother of 10 children, the last being born four years previously. Her last menstrual period ended during the first week of March 1911. All her past labours had been iincomplicated and her pelvic measurements were above the average. She was admitted as an emergency case into the City of London Lying-in Hospital on December 30 midnight (11-55p.m.). Labour had started a t 10a.m. the same day with escape of the liquor amnii. On admission her pulse-rate was 84 and temperature 99°F. The uterine contractions were very infrequent, and the 0s was about the size of half-a-crown. The child presented by the face in the second position. The fcletal heart was not heard. As her condition was that of uterine inertia 20grs. chloral hydrate were administered, after which she dozed and slept for some hours. During the morning of the 21st her condition remained much the same, the pains still being infrequent, and the 0s dilated slowly, not being fully dilated till midday. At 1 p.m. it was noticed that her pulse-rate was 116, and 2-30, when I saw her, it had risen to 132 without any apparent reason, and with this exception the patient's condition was not urgent. The uterus was soft and not tender, nor were its contractions severe; no ring could be felt, though, owing to the thickness of the patient's abdominal wall it might have been present and yet have escaped detection. I deemed it advisable to deliver the patient, and the forceps was applied to the face under CHC1,. The head was easily brought down to the outlet, the chin rotated forwards, but the utmost difficulty was experienced in bringing the head over the perineum, and it was not until one blade of the forceps was used as a vectis that the head was completely delivered. The cause of this difficulty was now evident as the shoulders of the child were detained above a thick ring which encircled the lower part of the neck. The child was dead and its skin stained by meconium.To have performed an embryotomy would have been extremely difficult and the results of this operation in previous cases had seemed to me to be unsatisfactory so that I determined to try the effect
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.