A Revision of the Seed Impressions of the British Coal Measures

Abstract

T HE occurrence of a variety of impressions or casts of seed-like bodies in the British Coal Measures has been known since the days of John Woodward 1 ( 1729), yet at the present time there is probably no set of Coal Measure fossils which stands in greater need of systematic revision than these. The most recent list of such objects, published by Dr. Kidston a in 1894, includes only five genera with nineteen species from the whole of the British Coal Measures. Of these genera one, Carpolithus, containing nearly one-third of the total number of species, is nondescript, and amounts to little more than the word ' seed'. It is a useful term under certain circumstances, but should be regarded only as a temporary expedient. There is little doubt, I imagine, that the Coal Measure seeds which have been referred to this genus are of several fundamentally distinct types.When determining Coal Measure fossils, one frequently finds that, while there is no hesitation as to the specific assignment of a particular seed, there is often doubt as to whether such and such a species really belongs to the genus to which it has commonly been assigned, and especially whether it possesses any real morphological affinity to the other species contained therein. In my own case, however, I have found it necessary to defer any opinion on such questions until an opportunity should occur for re-investigating the grouping of Coal Measure seeds in general.In attempting this difficult task here, I am well aware that the principles on which a nomenclature should be founded are to some extent matters of opinion, and that in some cases differences of opinion are likely to arise as to matters of fact. The botanical interpretation of the features exhibited by a particular impression is sometimes by no means an easy > Woodward (1729), p. 53.• Kidston (9i).[A n nnl« of Botany, VoL XXVIII. No. CIZ. January, GArber.-A Revision of Ihe Seed Impressions of tltetask, yet it is on these grounds that a classification should be based. In my opinion one of the most fundamental distinctions among Coal Measure seeds should be founded on the symmetry. We know from the study of petrified specimens that most of these fossils belong to two distinct types, the Radiosperms and the Platysperms, as F. W. Oliver 1 pointed out in 1903.The former are symmetrical in more than two planes, the latter in only two or in a single plane. At the same time a classification based solely on symmetry is not ideal. Certain seeds, such as Trigonocarpus Parkinsoni, are radiospermic from one point of view, and platyspermic from another.Although the number of such cases is few at present, an intermediate class may have to be recognized eventually. 2 The main difficulty as regards the recognition of the type of symmetry among impressions arises, of course, from the compression which many seeds have undergone before or during fossilization. From an isolated example it may be sometimes impossible to determine whether the seed in question is radiospermic or platyspermic, especially if it be a new ...

Sementes do gênero Samaropsis Goeppert no Permiano inferior da bacia do Paraná, Sul do Brasil

“…Segundo Millan (1994), o gênero Samaropsis é caracterizado pela diferenciação evidente da testa em uma delicada e externa sarcotesta em contraposição a uma inflexível e interna esclerotesta, assim como fora definido por Arber (1914). Entretanto, a presença ou não de uma testa diferenciada depende diretamente do estado de preservação dos espécimes.…”

“…Recentemente, Archangelsky (2000:102), em extensa revisão, e analisando as argumentações de autores como Arber (1914), Seward (1917), Florin (1940), Maithy (1965) e Millan (1977b, ampliou a diagnose de Samaropsis, definindo-o como "semillas bilateralmente simétricas con uma sarcotesta ancha que envuelve total o casi totalmente la esclerotesta".…”

Pteridophytic features in some Lower Carboniferous seed megaspores

“…Mention must be made of the work of Arber (1914) and of Crookall (1933) who recommend that compressions of bicornute seeds possessing many of the features of S. bicaudata be included in the genus Cornucarpus Arber. However, the genus as originally defined by Arber (1914) could not include seeds with a conspicuous lateral wing.…”

XII.—On Salpingostoma dasu: A New Carboniferous Seed from East Lothian

“…casts of the inner surface of the sclerotesta in Trigonocarpus parkinsoni range from 180-280 mm. (Arber, 1914).…”

“…Two of the forms to which reference should be made were described by Arber (1905) under the titles Lagenostoma kidstoni and L. sinclairi respectively, from the Lower Coal Measures of Scotland. They are both small seeds, the former probably naked, but the latter with a well-marked cupule.…”