The region encompassing the Sahara and the Arabian Peninsula has seen dramatic changes in Holocene moisture availability. While the highlands of Yemen are sensitive to moisture dynamics, their history remains poorly known. This study provides new information on Holocene environmental change in the Yemeni highlands through analyses of the lithostratigraphy and ostracod stratigraphy of two localities. The diversity and abundance of ostracod populations serve as key environmental indicators, reflecting stability and change in aquatic habitats. Six time periods are identified, each representing distinct phases of environmental and climatic change. Undated gravelly fine sands, possibly of late-glacial or Early Holocene age, indicate dry conditions. Subsequent stages indicate a progression of moister conditions and warmer climates characterized by the formation of ponds and lakes and fluctuations in water availability. Shifts occurred between oligotrophic and eutrophic conditions, and between desiccation trends and wetter conditions. We found the taxonomic composition of ostracod populations in Yemen’s highlands to include species from mountainous regions of Africa and the broader Palaearctic. This research aligns with previously reported data and expands our understanding of past ecosystems and climatic conditions in highland Yemen.

The Recent ostracods from the tidal flats of Al-Hudeida City, situated at the southern tip of the Red Sea have been studied. Thirty-eight species belonging to 32 genera could be identified. One new species, Hiltermannicythere hishamalii, is described. The assemblage of the fauna shows a close similarity to the Indo-Pacific region, especially to the east coast of Africa and the Persian Gulf.

Lake or marsh sediments in the Qa'a Jahran-Dhamar area indicate a period of higher moisture availability in the early Holocene of the highlands of Yemen. Forty-two marl-peat sediment samples from eight stratigraphic sections of that area have been collected and are examined for the first time for their ostracod associations. Eight species belonging to seven genera and four families are reported. Their ecological tolerances and preferences are used to investigate the climatic and environmental changes in the early to mid-Holocene. Our data are compared and correlated with previous archaeological results, particularly from the region of Qa'a Jahran (Dhamar) in the vicinity of the village of Beyt Nahmi. We conclude that the wettest period of the Holocene was from about 7900 to 7400 cal yr BP, when northwards incursion of the Indian Ocean Monsoon caused intensified monsoon precipitation over southern Arabia.

One hundred and eleven benthic foraminiferal species belonging to 36 genera, 25 families, 16 superfamilies and 4 suborders were identified from twenty samples collected from Bir Ali beach on the Yemeni Arabian Sea coastline. The benthic foraminifera assemblages were dominated by species belonging to Miliolina suborder with 71 species and 17 genera, followed by Rotaliina with 29 species and 14 genera, Textulariina 9 species and 3 genera and Lagenina 2 species and 2 genera. The distribution of recent shallow-water benthic foraminifera in surface sediment samples is in varians from sample to another. Higher abundance of genus Quinqueloculina is recorded in almost all the samples of the study area. The recorded assemblages show a high similarity to the foraminiferal assemblages of the Indo-Pacific region, East African coast and Red Sea.

A new marine genus of Ostracoda from the tidal flats of Aden City is erected and one new species is described. The systematic position of the present taxon is discussed.

Eleven species belonging to ten genera of fresh water Ostracoda, have been identified from thirteen sediment samples collected from the bottom of permanent streams running along the N-NE part of Socotra Island. The fauna shows close affinity with the S-E African and S-E Asian assemblages, with interesting findings regarding the Palearctic Limnocythere stationis Vávra, 1891. The taxonomy and geographic distribution of the fauna are here discussed in detail.

Forty-seven species belonging to 30 genera of ostracods have been identified from Recent shallow marine sediments collected along the northern coastline of the island of Socotra (Indian Ocean). The systematics and distribution of these ostracods are discussed. Three genera, Loxoconcha, Bosasella, and Xestoleberis are found to have high species diversity. The species Loxoconcha ghardaqensis, Moosella striata are best documented in the Red Sea and Gulf of Aden while Kotoracythere inconspicua and Triebelina sertata were found to be the most widespread species. The fauna shows a close affinity to other ostracod assemblages of the Indo-Pacific region, East African coast and Red Sea.

A total of 45 genera and 64 species of ostracods have been identified from nine shallow marine sediments ranging in depth from 0.40 to 1 m, collected along the coast line of Aden, Little Aden and Amran volcanic peninsulas. A systematic study of these ostracods is presented in this paper. One new genus, Microhoweina, is erected, and five new species, Corallicythere adenensis, Cytherella brettingi, Microhoweina elongata, Neocytheromorpha tawahinsis and Paracytheroma abyanensis, are described. The fauna shows a close similarity to other ostracod assemblages of the Indo-Pacific, East and West African coasts and Red Sea regions. Tanella gracilis Kingma 1948 and Kotoracythere inconspicua (Brady 1880) are the most abundant species.