Paskapoo Formation Research Articles

New craniodental material of Pronothodectes gaoi Fox (Mammalia, “Plesiadapiformes”) and relationships among members of Plesiadapidae

Plesiadapidae are a family of Paleogene mammals thought to have phylogenetic affinities with modern Primates. We describe previously unpublished dentitions and the first skull and isolated petrosals of the plesiadapid Pronothodectes gaoi, collected from middle Tiffanian localities of the Paskapoo Formation in Alberta. Other species of Pronothodectes, traditionally considered the most basal members of the Plesiadapidae, occur at earlier, Torrejonian horizons in Montana, Wyoming, and Alberta. Classification of P. gaoi as a species of Pronothodectes has proved controversial; accordingly, we use the newly available samples and the more extensively preserved specimens to re-evaluate the generic affinities of this species. Included in our study are comparisons with craniodental material known for other plesiadapids and plesiadapiforms. Cladistic analysis of craniodental characters is used to assess the hypothesis that P. gaoi and other species in this genus are basal members of the Plesiadapidae. The new dental evidence confirms that P. gaoi lacks derived character states of other plesiadapids except for a variably present fissuring of the m3 hypoconulid. Moreover, several aspects of the cranium seem to be more primitive in P. gaoi (i.e., more like nonplesiadapid plesiadapiforms) than in later occurring plesiadapids, such as Plesiadapis tricuspidens and Plesiadapis cookei. Cladistic analysis of craniodental morphology supports a basal position of P. gaoi among species of Plesiadapidae, with the exception of other species of Pronothodectes. The basicranium of P. gaoi preserves a laterally placed bony canal for the internal carotid neurovascular system, suggesting that this was the ancestral condition for the family.

An Unusual Early Primate from the Paleocene Paskapoo Formation, Alberta, Canada

A new plesiadapiform primate, Phoxomylus puncticuspis gen. et sp. nov., is described based on an isolated but well-preserved upper molar from the early Tiffanian (late Paleocene) Cochrane 2 locality, southwestern Alberta, Canada. Although possessing a robust postprotoconal fold, an unambiguous synapomorphy of primates, Phoxomylus differs from other plesiadapiforms in its retention of primitive molar features, including acutely pointed major cusps and sharp crests, deep trigon basin, and lack of the bunodont coronal specializations that purportedly marked the transition from insectivorous non-primate ancestors to omnivorous/frugivorous basal primates. Coronal features of the holotype of P. puncticuspis imply that during mastication the mandible was adducted in a near-vertical plane, with little capacity for the transverse movement that is already seen in molar morphology of the earliest and most basal plesiadapiform, Purgatorius. Instead, molar morphology in P. puncticuspis implies emphasis on vertical pie...

Edworthia Lerbekmoi, a New Primitive Paromomyid Primate from the Torrejonian (Early Paleocene) of Alberta, Canada

A primitive paromomyid plesiadapiform primate,Edworthia lerbekmoinew genus and species, is described from a recently discovered locality in the Paskapoo Formation, exposed at a road cut in Edworthy Municipal Park, Bow River Valley, Calgary, Alberta, Canada. The new taxon, probably middle Torrejonian (To2) in age, is based on two dentary fragments containing well-preserved dentitions that bracket p2-4, m1-3. With the exception of the basalParomomys, E. lerbekmoidiffers from all other paromomyids in retaining p2, but p2 in the new paromomyid is single-rooted, not two-rooted as inParomomys. E. lerbekmoidiffers further fromParomomysin having an enlarged anterior alveolus for a tooth immediately anterior to p2, hypothesized to be il. Unlike other paromomyids with an enlarged il, however, this tooth inE. lerbekmoiwas obliquely, not horizontally, oriented and its alveolus opens dorsally, in the alveolar row, not anteriorly, as in other paromomyids in which il is greatly enlarged. This suggests thatE. lerbekmoirepresents a previously unknown paromomyid lineage that evolved from an ancestor having obliquely oriented lower incisors as in the basal primatePurgatorius, not from an ancestor in which il was already subhorizontal in orientation, as inParomomys.If this working hypothesis is correct or whether in the future some other evolutionary scenario will better account for the unique anterior dentition inE. lerbekmoi, the new paromomyid nonetheless demonstrates that crucial aspects of the earliest history of the important plesiadapiform family Paromomyidae remain to be discovered.

Hydrogeological implications of paleo-fluvial architecture for the Paskapoo Formation, SW Alberta, Canada: a stochastic analysis

Fluvial systems tend to deposit sediment in well-defined relational geometries and in vertically and laterally repeating patterns. These sedimentary deposits are preserved to varying degrees depending on how much the fluvial system reworks the deposits. The Paskapoo bedrock aquifer system in southern Alberta, Canada, was deposited in a foreland depositional basin during uplift of the Rocky Mountains, and both the geomorphic model and field evidence indicate that the upper 100 m of the local aquifer system contains well-preserved, highly connected paleo-channels and associated overbank deposits. In order to evaluate the value of different types of data, a simplified stochastic-numerical groundwater flow model was developed to examine the sensitivity of results to model parameters. Parameters examined include: fraction of the formation made up of channel sands; meander and sinuosity factors; width-to-depth ratios of preserved channels; and crevasse splay conductivity. In all cases examined, the system exhibited anisotropic behavior with the along-channel flow direction being the most permeable and the vertical direction being least permeable. In general, the strongest control on the resulting effective anisotropic hydraulic conductivities was channel fraction, but geometric factors that control between-channel connectivity (e.g., channel sinuosity) had an appreciable effect on the across-channel flow direction effective permeability.

Influence of till provenance on regional groundwater geochemistry

Abstract A regional groundwater geochemistry study was conducted in the Paskapoo Formation of southern Alberta, Canada. Our study area focused on a region where two continental ice sheets, the Cordilleran and Laurentide met. The glacial deposits transported by these ice sheets have different bulk characteristics reflective of the bedrock of the source region of the ice. Recharge through these two different glacial deposits generates distinctly different water geochemistry within the underlying Paskapoo Formation, such that bedrock aquifer acquires a geochemical signature of the immediately overlying glacial deposits through which recharge occurs. Oxidation of pyrite in Laurentide till generates high-sulphate groundwater, and associated acid generation leads to enhanced mineral weathering. This generates high TDS high Na–SO4 groundwater in underlying bedrock aquifers. This process appears transitory, where thin Laurentide drift deposits are completely oxidized and have reduced capacity to generate high-sulphate water. The same bedrock underlying carbonate dominated Cordilleran drift deposits have low TDS Ca–HCO3 groundwater.

Regional characterization of the Paskapoo bedrock aquifer system, southern AlbertaGeological Survey of Canada Contribution 2008-0479.

The Paskapoo Formation of southern Alberta supports more groundwater wells than any other aquifer system in the Canadian Prairies. Located in a region of rapid population growth and straddling watersheds where no new surface water licenses are available, this aquifer system is under increasing pressure to provide water supply. The Paskapoo Formation represents a foreland deposit of a siltstone- and mudstone-dominated fluvial system. The system is highly heterogeneous with broad ranges in physical properties that impact groundwater production. High-porosity coarse-grained channel sandstone can provide productive wells, whereas thin and fractured sands and siltstones are low producers. The basal Haynes Member and western portion of the Paskpaoo Formation have higher sandstone volumes than other portions of the system. Fracture density shows a strong inverse relationship to bed thickness, such that fracture flow becomes more important for thinner sandstone beds. There is no regional-scale flow system associated with the Paskapoo Formation; rather it is dominated by local-scale recharge processes. The geochemistry of Paskapoo Formation groundwater is largely controlled by the variable composition of immediately overlying glacial deposits.

Magnetobiostratigraphy of the continental Paleocene upper Coalspur and Paskapoo formations near Hinton, Alberta

Abstract An integrated magnetostratigraphic and palynostratigraphic study of the continental, mostly lower Paleocene upper Coalspur and middle to upper Paleocene Paskapoo Formation was carried out in the Coal Valley to Hinton area of west-central Alberta. Magnetostratigraphic samples were taken from 2 cores and one outcrop in the Coal Valley Mine, a roadcut at Coalspur, the Bryan Creek Mine pit near Robb, 13 outcrop locations, and 4 cores in the Hinton-Obed Mountain area (totaling 313 samples). About 300 palynostratigraphic samples were taken from cores and outcrops within Coal Valley Mine, Coalspur roadcut, Bryan Creek Mine, the Hinton area and Obed Mountain and vicinity. Sample localities were structurally fitted into a composite Paleocene section from the Cretaceous-Tertiary boundary to the top of the No. 1 coal in the Obed Mountain Mine, totaling about 300 m of upper Coalspur and about 770 m of Paskapoo Formation. The section encompasses parts of magnetozones 29r to 24r and palynozones Wodehouseia spinata Zone, Aquilapollenites reticulatus Subzone through the Pistillipollenites mcgregorii Zone. Preserved sediment accumulation rates were up to about 250 m per m.y., but averaged much less due to hiatuses. These hiatuses involve the omission of parts of magnetochrons 28r, 28n and 27r in the Arbour-Val d’Or coal zone, 27n at the base of the Paskapoo, and 26n in the upper Paskapoo, totaling at least 2.2 m.y.

Hydraulic, water quality, and isotopic characterization of Late Cretaceous-Tertiary Ardley coal waters in a key test-well, Pembina-Warburg exploration area, Alberta, Canada

Abstract A detailed evaluation of the hydraulic parameters and formation fluids of a key test-well completed in the uppermost Ardley coal was undertaken in the Pembina-Warburg exploration area, Alberta Basin, Alberta, Canada. The testing method isolated the target coal zone from the overlying Paskapoo Formation with an intermediate casing set in the coal. Measurements showed a build-up of fluid (water) pressure within the coal to approximately 1,470 kPa. Detailed hydrogeological testing showed that the permeability of the coal is clearly less than 5 mD and likely on the order of 1 mD. Formation waters sampled during the drawdown and build-up phases were Na-HCO3 type with salinities of approximately 1,920 mg/L TDS (calculated). Sodium and chloride concentrations were approximately 835 and 250 mg/L, respectively. Detailed analyses of the formation waters showed that dissolved and total trace metal concentrations fall within Canadian drinking water quality standards with the exception of iron and manganese. Organic compounds including monocyclic aromatics (Benzene, Toluene, Ethyl-benzene, Xylene, BTEX) were not detected, with the exception of trace toluene concentrations. Anomalously high bicarbonate concentrations of up to 1650 mg/L (δ13CDIC +22.50 ‰) and dissolved methane concentrations of up to 36 mg/L (δ13CCH4 −48.32 ‰) point to the presence of secondary biogenic gas. Formation waters are non-tritiated; δ18O and δ2H values plot along the local groundwater line for Edmonton, Alberta indicating a meteoric origin. Data from the test-well suggest that depressurization (i.e., diversion of fluids) of the coal zone is necessary for gas production. If depressurization is contained to within the coalbeds, relatively small quantities of produced fluids would be anticipated. Although most of the groundwater for consumption within the immediate area of the test well is obtained from shallower parts of the flow systems in the uppermost parts of the Paskapoo Formation, under the current regulatory framework a Preliminary Groundwater Assessment as defined by the Alberta Environment and the EUB (2004) would be necessary prior to diversion.

HOROLODECTES SUNAE, AN ENIGMATIC MAMMAL FROM THE LATE PALEOCENE OF ALBERTA, CANADA

A new eutherian mammal of uncertain taxonomic position is described on the basis of well-preserved dental and gnathic specimens collected from localities in the Paleocene Paskapoo Formation of Alberta, Canada. Horolodectes sunae new genus and species is represented by seven incomplete maxillae, eleven incomplete dentaries, and numerous isolated teeth, together preserving nearly all of the postcanine dentition. The unusual dentition of Horolodectes n. gen. consists of trenchant, posteriorly leaning premolars in combination with comparatively primitive molars, suggestive of a masticatory cycle that consisted primarily of shearing and, to a lesser degree, horizontal grinding. Included among the specimens of Horolodectes is an incomplete dentary of an immature individual, with the teeth having been in various stages of eruption at the time of death. Although the dentition of Horolodectes broadly resembles that of apheliscine hyopsodontids, pentacodontine pantolestids, and “ungulatomorphs” among eutherian mammals, significant differences in the coronal structure of the teeth prevent unequivocal referral of Horolodectes to any of these groups, or to any known eutherian order.

NEW NEOPLAGIAULACID MULTITUBERCULATES (MAMMALIA: ALLOTHERIA) FROM THE PALEOCENE OF ALBERTA, CANADA

Neoplagiaulacid multituberculates are among the most numerous and best represented members of early Cenozoic North American mammal faunas, achieving their greatest diversity during the Paleocene. Despite their relatively dense record in the Torrejonian (middle Paleocene) and Tiffanian (late Paleocene), the study of early Cenozoic neoplagiaulacids has been limited more often than not to isolated teeth or, more rarely, incomplete skull, gnathic, or postcranial remains. The current study reports on new neoplagiaulacid multituberculates from the Paleocene Paskapoo Formation of central Alberta, Canada, at localities along the Blindman River near the City of Red Deer. The exceptionally well-preserved specimens consist of incomplete articulated and associated skull and gnathic remains, and collectively document four new species: Ectypodus elaphus, Neoplagiaulax serrator, Neoplagiaulax paskapooensis, and Neoplagiaulax cimolodontoides. Neoplagiaulax paskapooensis is the most dentally complete neoplagiaulacid so far discovered, with a single specimen documenting for the first time left and right I2 and I3 in situ with the cheek teeth, along with the associated lower dentition. Specimens of Neoplagiaulax cimolodontoides record important details of the rostrum and palate, and provide the first direct evidence of incisor replacement in Neoplagiaulax. The new neoplagiaulacids, together with other multituberculates from the Blindman River localities, document unusually high multituberculate diversity in the latter half of the Tiffanian in western Canada. Despite superficial similarity to some European species of Neoplagiaulax, the new taxa from the Paskapoo Formation apparently show no closer relationship to these than do other North American congeners, suggesting parallel evolution in endemic North America and western European clades.

WINDOWS ON THE EVOLUTION OF PICRODUS (PLESIADAPIFORMES: PRIMATES): MORPHOLOGY AND RELATIONSHIPS OF A SPECIES COMPLEX FROM THE PALEOCENE OF ALBERTA

Since 1908, the peculiar North American primate Picrodus Douglass, 1908 (Picrodontidae; Plesiadapiformes) has been thought to contain only a single species, P. silberlingi Douglass, 1908, of late Paleocene age. However, new collections from the Paskapoo Formation, Alberta, Canada, reveal that instead a rich complex of Picrodus species lived during the Paleocene. Three of these, Picrodus calgariensis, P. canpacius, and P. lepidus, are described herein as new. Others, represented by more fragmentary specimens from Canada and the United States, are included in this paper, but are not named. P. calgariensis, from Who Nose? (late Torrejonian), Calgary, is the most primitive known species of Picrodus, having molars with little crenulation of the enamel. P. canpacius, from Cochrane 2 (earliest Tiffanian), northwest of Calgary, most resembles P. silberlingi sensu stricto, but differs in P4 structure, denser enamel crenulation, and weaker molar cusps. P. lepidus, from DW-2 (middle Tiffanian), near Red Deer, is the most advanced, having, for example, a two-rooted P4, tiny p3, and single-rooted p4. At least two of these species also occur in the United States, documented by fossils referred to P. silberlingi by previous workers. Dental evolution within Picrodus seems marked by several trends, including increase in size of i1, simplification of P4, reduction of molar cusps and crests, enlargement of the horizontal occlusal surfaces of the molars, and greater crenulation of enamel. From present knowledge, Zanycteris paleocenus Matthew, 1917 is dentally more primitive than Picrodus, Draconodus Tomida, 1982 is a valid genus, and picrodontids probably originated from “purgatoriid-grade” plesiadapiforms in earliest Paleocene time.

Preliminary hydrogeological assessment of Late Cretaceous–Tertiary Ardley coals in part of the Alberta Basin, Alberta, Canada

A preliminary hydrogeological evaluation was undertaken on the gas potential of shallow coals in the Pembina–Warburg exploration area in the Alberta Basin, Alberta Canada. Regional data for the Late Cretaceous–Tertiary Ardley Coal Zone (ACZ) were compiled and supplemented with site-specific data collected from a key test- well drilled as part of a regional exploration program. Limited regional pressure data suggest hydraulic communication between the uppermost Ardley with the overlying Paskapoo Formation. A comparison between hydraulic head and topography suggests that flow, at least in part of the Ardley–Paskapoo, is gravity driven. However, a decoupling of the hydraulic regime appears evident from pressure test data in beds stratigraphically below the uppermost Scollard (Ardley) and above the base of Scollard at least in the eastern part of the study area where the test-well was drilled. The decoupling is evident in regional pressure data but the precise stratigraphic position may vary. Regionally, formation waters typically are Na–HCO3 type with salinities (as TDS) of less than 2000 mg/L. Anomalously high bicarbonate (dissolved inorganic carbon or DIC) concentrations exceeding 1500 mg/L with δ13CDIC + 22.50‰ and dissolved methane identified in formation waters collected directly from Ardley coal in test-well 103 point to the presence of secondary biogenic gas. The 13C isotopes for DIC, coupled with 18O and 2H isotopes for associated groundwater and regional hydraulic data, suggest that the uppermost Ardley Coal Zone in the eastern part of the study area is part of a regional, topographically driven, dynamic flow system in which methanogenic processes are modifying groundwater chemistry and gas charging parts of the area. Whether or not biogenic gas-charging in the Ardley is pervasive is uncertain. The relatively small coal data set requires that further exploration in the study area should consider the presence of microbial gas and the potential for hydrogeological controls on its distribution. However, further detailed testing will be necessary to develop a consistent and useful database for exploration and development.

A new species of the ptilodontid multituberculate Prochetodon (Mammalia, Allotheria) from the Paleocene Paskapoo Formation of Alberta, Canada

A new species of the ptilodontid multituberculate genus Prochetodon (Mammalia, Allotheria) from the Paleocene Paskapoo Formation of Alberta, Canada, is described. Prochetodon speirsae sp. nov. is the oldest discovered species of the genus, extending the temporal range of Prochetodon earlier into the Paleocene. It exhibits a mosaic of primitive and derived dental features suggestive of a position phylogenetically intermediate between Ptilodus and Prochetodon. Newly discovered specimens from the late Paleocene Gao Mine locality are referred tentatively to Prochetodon foxi. The occurrence of a primitive form of Prochetodon in sediments of early Tiffanian age suggests the evolutionary history of the genus is more complex than previously appreciated. Prochetodon joins a number of well-documented, progressive mammalian taxa making their first appearance in the Western Interior of North America at higher latitudes, well before their first known occurrence in the United States, suggesting a possible origin and immigration from currently unsampled habitats.

New Ichnotaxa of Mammal and Reptile Tracks from the Upper Paleocene of Alberta

Only two vertebrate trackways are known from the Paleocene of western Canada and are among the few Paleocene vertebrate trackways known worldwide. A natural cast trackway consisting of five prints (three pes, two manus) on a fallen block was found along the Red Deer River, near the town of Red Deer, Alberta, in 1927. The discoverers, Ralph Rutherford and Loris Russell, identified the strata the track block had fallen from as belonging to the Paskapoo Formation (upper Paleocene: middle Tiffanian). The trackway was attributed to a mammalian track-maker in two subsequent publications. However, the prints are more characteristic of a reptilian (crocodylian) track-maker. A natural cast track-bearing block was discovered on Signal Hill in the city of Calgary during the preparation of a new residential subdivision in 1990. The large track-bearing block was found in a rock pile but is suspected to have originated from strata belonging to the Porcupine Hills Formation (Upper Paleocene: late Torrejonian), which was being excavated at the time. This large slab contains twelve prints (six pes, six manus) and is associated with extensive mud cracks. The mammalian affinity of the trackmaker was recognized by researchers from the Royal Tyrrell Museum of Palaeontology.

Late Torrejonian (middle Paleocene) mammals from south central Alberta, Canada

The Paskapoo Formation in central and south central Alberta, Canada, preserves continental sediments of Paleocene age. Outcrops of the formation on Nose Creek in northeast Calgary, at a locality called Who Nose?, have yielded fossil mammals from the middle part of the epoch. To date, some 400 dental specimens representing eight mammalian orders have been recovered, among them numerous well-preserved jaws. Newly named taxa include new species ofParectypodusandBaiotomeus(Multituberculata); new species ofParectypodus, Litomylus(Condylarthra), andCyriacotherium(Pantodonta) are left unnamed. Biostratigraphic correlation indicates a late Torrejonian age for the local fauna based on the presence of the plesiadapid primatePronothodectes matthewi. Faunal comparisons suggest a close similarity to the penecontemporaneous Gidley Quarry fauna, Montana, with a taxonomic diversity consistent with other co-eval faunas in the Western Interior of the United States. The specimens from Who Nose? constitute the largest collection of Torrejonian mammals from Canada, offering a unique perspective on mammalian diversity from an otherwise poorly represented interval in western Canada.

LATE TORREJONIAN (MIDDLE PALEOCENE) MAMMALS FROM SOUTH CENTRAL ALBERTA, CANADA

The Paskapoo Formation in central and south central Alberta, Canada, preserves continental sediments of Paleocene age. Outcrops of the formation on Nose Creek in northeast Calgary, at a locality called Who Nose?, have yielded fossil mammals from the middle part of the epoch. To date, some 400 dental specimens representing eight mammalian orders have been recovered, among them numerous well-preserved jaws. Newly named taxa include new species of Parectypodus and Baiotomeus (Multituberculata); new species of Parectypodus, Litomylus (Condylarthra), and Cyriacotherium (Pantodonta) are left unnamed. Biostratigraphic correlation indicates a late Torrejonian age for the local fauna based on the presence of the plesiadapid primate Pronothodectes matthewi. Faunal comparisons suggest a close similarity to the penecontemporaneous Gidley Quarry fauna, Montana, with a taxonomic diversity consistent with other co-eval faunas in the Western Interior of the United States. The specimens from Who Nose? constitute the largest collection of Torrejonian mammals from Canada, offering a unique perspective on mammalian diversity from an otherwise poorly represented interval in western Canada.

Amia cf. pattersoni from the Paleocene Paskapoo Formation of Alberta

A well-prepared anterior half of an amiid skull from the Late Paleocene Paskapoo Formation of south-central Alberta is described. The specimen is either very closely related to, or conspecific with, Amia pattersoni Grande and Bemis, 1998, from the Early Eocene Green River Formation of Wyoming. We leave the specimen as Amia cf. pattersoni until additional material is found to further clarify its relationships. Amia cf. pattersoni is the oldest known specimen clearly identifiable as belonging to the genus Amia (sensu Grande and Bemis, 1998), and the Paskapoo species extends the known geographic range of Amia both northward and westward. The fish assemblage of the Paskapoo Formation represents the most diverse freshwater Paleocene fish fauna known from North America. Based on comparisons of sample size and relative taxonomic diversity to the better known Green River Formation localities of Wyoming, we predict that further collecting will substantially increase the known diversity of the Paskapoo fauna. The Paskapoo Formation, therefore, has great potential to continue adding to the meager knowledge of pre-Eocene freshwater teleost diversity in North America.

Geological setting and paleobotany of the Joffre Bridge Roadcut fossil locality (Late Paleocene), Red Deer Valley, Alberta

The Joffre Bridge Roadcut locality (Paskapoo Formation) in south-central Alberta yields plant, mammal, fish, and insect fossils. A Late Paleocene (Tiffanian) age is indicated by mammalian fossils, supported by magnetostratigraphy and palynostratigraphy. This paper summarizes the flora (28 taxa have been identified to date) and describes the sedimentology to provide a paleoenvironmental context. Outcrops at the site are limited, but seven stratigraphic units are recognized and are interpreted to represent five environments of deposition: flood plain, fluvial channel, abandoned channel, swamp, and crevasse splay. The flood-plain mudstones lack identifiable plant material due to bioturbation and pedogenesis. They are capped by a thin, clay-rich paleosol with scattered vertebrate bones. An upward-fining sequence, interpreted as fluvial channel and channel abandonment sediments, rests directly on the paleosol and includes remains of riparian trees. Carbonaceous mudstone, interpreted as a swamp facies, includes remains of only five taxa (taxodiaceous conifers and riparian trees). Light-coloured mudstones on top of the swamp facies include a more diverse assemblage (aquatic and understory plants, taxodiaceous conifers, and riparian trees). Those beds are interpreted as the distal margin of an encroaching crevasse splay. Overlying sediments coarsen upward and are unfossiliferous, except for one occurrence of articulated fish skeletons from a mass-death event. The most productive beds for plant fossils are the top of the channel-abandonment sequence, the swamp horizon, and the base of the crevasse splay. Those beds have also yielded some insect, fish, and mammal remains.

Morphology and paleoecology of Ricciopsis speirsae sp.nov. (Ricciaceae), a fossil liverwort from the Paleocene Joffre Bridge locality, Alberta, Canada

More than 60 specimens of a fossil liverwort gametophyte have been recovered from the Paleocene Paskapoo Formation at the Joffre Bridge locality near Red Deer, Alta. They closely resemble thalli of extant Riccia and have been assigned to the genus Ricciopsis Lundblad. Thalli are linear and prostrate, with smooth margins and a distinct dorsal sulcus. Dichotomous branching occurs in a single plane. Ribbonlike segments reach lengths as great as 55.0 mm, with up to seven dichotomies. Width is typically 1.5–2.0 mm, but abrupt constrictions and dilations are sometimes present proximal to dichotomies. The latter feature distinguishes this fossil from known fossil and living Ricciaceae, and thus it is referred to a new species, Ricciopsis speirsae sp.nov. Liverworts are not common in the fossil record. Ricciopsis speirsae is the first ricciaceous fossil to be described from North America and the first of Paleocene age worldwide. The specimens are found in a layer of lacustrine claystone, scattered among remains of a free-floating lemnaceous plant. Both the geologic setting and the associated fossils indicate that the environment of deposition was a shallow oxbow lake. Key words: Ricciaceae, Riccia, Ricciopsis, liverwort, Paleocene, fossil.

The fossil monocot Limnobiophyllum scutatum: Resolving the Phylogeny of Lemnaceae

More than 200 specimens of Limnobiophyllum scutatum (Dawson) Krassilov have been recovered from lacustrine claystones in the Paleocene Paskapoo Formation near Red Deer, Alberta. The plant was a floating, aquatic angiosperm with helically arranged, ovate leaves attached in small rosettes. Rosettes are interconnected by stolons and bear simple adventitious roots as well as larger branching roots that appear to have vascular tissue. Leaves are pubescent, aerenchymatous, with 12-14 campylodromous primary veins that curve toward the apex, joining a fimbrial vein, often an apical notch. Staminate flowers with two, four-loculate stamens, are borne in the axils of second leaves. Anthers contain monoporate, globose, echinate pollen, 20-25 µm in diameter. The pollen wall is 0.8 µm thick, with a homogeneous foot layer, granular to slightly columellate infratectal layer and an echinate tectum. Pollen most closely resembles the sporae dispersae genus Pandaniidites Elsik. The completeness of L. scutatum has allowed for its inclusion in a numerical cladistic analysis to resolve relationships among taxa of the Lemnaceae, Pistia, and selected genera of Araceae. Results of the analysis indicate that the Lemnaceae plus Pistia form a monophyletic group within the Araceae.