Middle Cretaceous palynological assemblages rich in copepod eggs: their paleoecological significance

Abstract

The genera Nuculites and Cucullella have originated in different geographic areas, with the oldest record found in the Llandovery (Lower Silurian). The former was reported in Gondwana with two subgenera, Nuculites and Trilobonuculites, while the latter is found in Avalonia. Due to environmental and tectonic factors, those taxa became associated and distributed throughout Gondwana, Avalonia, Kazakhistan and Laurussia from the Late Silurian to the Late Devonian. The subgenus Trilobonuculites appeared firstly at the Pitinga Formation, Amazon Basin, Brazil, and the subgenus Nuculites is only recorded in the Silurian from the Tabuk Formation, Saudi Arabia. Cucullella was found in the Ross Brook Formation of New Scotia, Canada. Since the Late Silurian (Ludlow), which is marked by a marine transgression, Trilobonuculites and Cucullella started to occur associated, invading other paleocontinents, confirmed by the presence of Cucullella in the Gondwana (Bolivia) and Trilobonuculites in Avalonia (New Scotia). This suggests that the environment in these areas became more uniform due to the rise of the sea level and the narrowing of the ocean Rheic. The Silurian-Devonian boundary is marked by a marine regression followed by a new transgression, with maximum in the Frasian, and the collision of Avalonia/Baltica and Laurentia forming Laurussia. At this point, the subgenus Nuculites reappeared. Still in the Lower Devonian (Pragian-Emsian), the genus Nuculites diversified, dominating by the subgenus Trilobonuculites, while Cucullella was only represented by a sole species from Kazakhistan. In the Middle Devonian (Eifelian-Givetian) the subgenus Nuculites predominated while Trilobonuculites was restricted to the Maecuru Formation (Brazil). The only species of Cucullella dispersed to the oriental Laurussia and North and Occidental Gondwana. In the Late Devonian (Frasnian), the occurrence of these taxa was restricted to the Armorican Massif, Northeastern of Brazil and some doubtful occurrences in Bolivia. At that time, the oceans deepened, dysaerobic and anoxic environments spread out and Gondwana and Laurussia were approaching. These factors, associated with thermal stress, led to extinction of several taxa at the Frasnian/Fammenian boundary, including those studied here. The paleogeographic distribution of Nuculites and Cucullella agrees with the sea level curves and the movement of the continents suggested to have taken place during the Silurian and Devonian.-(

Early Miocene amber inclusions from Mexico reveal antiquity of mangrove-associated copepods

“… (1) Oman, Al Khlata Formation, Late Carboniferous (c. 303 Ma), harpacticoids 3 ; (2) United Kingdom, Kent, Holocene (Neolithic), harpacticoids 50 ; (3) USA, California, Early-Middle Miocene (13.4–19.3 Ma), harpacticoids and cyclopoids 4 5 6 62 63 ; (4) Argentina, Pleistocene, harpacticoids 5 ; (5) Canada, Saskatchewan and Alberta, Middle-Late Cambrian (488–510 Ma) 9 ; (6) USA, Tennessee, Middle-Late Cambrian (495–500 Ma) 10 ; (7) Sweden, Öland, Early Ordovician (477–485 Ma) 11 ; (8) Canada, Manitoba, Late Cretaceous (60–80 Ma) 36 ; (9) Spain, Álava, Early Cretaceous (100–120 Ma) 34 ; (10) Mexico, Chiapas, Early Miocene (22.8 Ma), harpacticoids (this study); (11) Brazil, Ceará, Early Cretaceous (110–120 Ma) siphonostomatoids 7 8 ; (12) Estonia, Latvia and European Russia, Middle–Late Devonian (358.9–387.7 Ma) 13 ; ( 13) Germany, Early Jurassic (190.8–199.3 Ma), crinoid cysts; (14) Germany, Late Jurassic (152.1–157.3 Ma), echinoid cysts; (15) Poland, Middle (163.5–166.1 Ma) and Late Jurassic (152.1–163.5 Ma), echinoid cysts 12 ; (16) France, Middle Jurassic (163.5–168.3 Ma), echinoid cysts 12 ; (17) France, Late Jurassic (157.3–163.5 Ma), crinoid and echinoid cysts; (18) Switzerland, Late Jurassic (157.3–163.5 Ma), echinoid cysts; (19) Israel, Middle Jurassic (163.5–166.1 Ma), echinoid cysts; (20) Dagestan, Turkmenistan and northern Caucasus, Middle Jurassic (163.5–166.1 Ma), echinoid cysts; ( 21) Germany, Holocene (Subboreal, 2.5–5 ka), spermatophores 22 23 ; (22) Denmark and West Greenland, Quaternary (late glacial (10–12 ka) and postglacial (0.5–5 ka), respectively), egg sacs 19 ; (23) northwestern Atlantic, Middle Miocene–Early Pleistocene (c. 0.78–15.97 Ma), eggs 16 ; (24) Mexico, Gulf of California, Holocene, eggs 17 ; (25) Brazil, Campos and Santos Basins, Early Cretaceous (100.5–113.0 Ma), eggs 24 25 26 ; (26) Australia, New South Wales, Holocene (5.63 ka), eggs 15 18 ; (27) Banda Sea, Late Pleistocene–Holocene, egg envelopes 20 21 . See ref.…”

“…Lesions apparent on Devonian sarcopterygian and placoderm fish in Latvia, Estonia and western Russia have been tentatively attributed to infestation by ectoparasites, including copepods 13 , however, since other causative agents are conceivable the association with copepods cannot be confirmed 14 . Subfossil copepod eggs 15 16 17 18 19 , egg envelopes 20 21 and spermatophores 22 23 have been reported from Neogene and Quaternary deposits and some acritarchs from the Lower Cretaceous in Brazil 24 25 26 and Florida 27 have been interpreted as copepod eggs.…”