![dinosaur battle realm dinosaur battle realm](https://i.ytimg.com/vi/Q9Q4pkNa5Zo/hqdefault.jpg)
This is the case with the North American dinosaur diversity record, which is skewed towards better preserved areas.Ĭurrently, North America provides the best available sampled, accurately dated, and stratigraphically continuous record of latest Cretaceous dinosaurs 5, and shows a decline in the numbers of genera and species from the Campanian to the Maastrichtian (Fig.
![dinosaur battle realm dinosaur battle realm](https://pbs.twimg.com/media/DtwO7sdW4AMgI_Q.jpg)
If the primary data that comprise the fossil record, for example, are spatially variable in completeness, then any attempt to extract a meaningful signal from this biased data set will tend to deliver a view of the past that is artefactual. Any palaeobiological investigation needs to take into account the completeness of the data set. Despite the widespread application of these techniques to a large range of fossil organisms, these methods are still heavily constrained by their inability to deal with the absence of data, especially when the spatial distribution of the fossil record in a particular time interval is strongly heterogeneous 15, 16. Others have attempted to utilise information on the evolutionary interrelationships of a fossil group in reconstructing palaeodiversity, via the inference of phylogenetic ghost lineages (e.g. Statistical methods developed to mitigate these biases typically employ subsampling (e.g. Biases include the incomplete preservation of delicate bones or soft-bodied animals, low preservation potential of some biotopes, erosion of fossil-bearing sedimentary rocks, and incomplete sampling by palaeontologists 13, which could lead to erroneous inferences, especially when compounded over geologic timescales. However, the extent to which these raw data have been biased by preservation and sampling artefacts has long been debated (e.g. Early attempts to determine deep time diversity dynamics were largely based on simple counts of the numbers of species (or higher taxa) in each time interval 9, 10. Choosing between these competing hypotheses, as well as the potential effects of environmental and tectonic processes on long-term diversity trends, remains a central goal of studies on dinosaur macroevolution and macroecology.įossils preserved in sedimentary rocks provide an invaluable record of life on Earth that has driven our understanding of macroevolutionary patterns, associated processes, and biodiversity through time.
#DINOSAUR BATTLE REALM DRIVERS#
One purported cause of this apparent decline has been linked to climatic drivers and habitat degradation 1, 8. 7 found evidence for a long-term (~40 million years) global decline of speciation rate in dinosaurs that began in the mid-Cretaceous, with the exception of ceratopsids and hadrosaurids, which apparently maintained a high diversification rate throughout the Late Cretaceous. Yet, these authors concluded that there was a latest Cretaceous (Campanian–Maastrichtian ~83–66 Ma) decrease in the diversity of large-bodied herbivores (primarily ceratopsid and hadrosaurid ornithischian dinosaurs), at least in North America 5, 6. A recent review argued that there is little evidence for a global, long-term decline 5. These can be simplified into two end-member scenarios: a sudden extinction or a gradual decline. In particular, a number of contrasting interpretations have been proposed regarding the diversity trends of dinosaurs in the lead-up to the Cretaceous/Paleogene (K/Pg) mass extinction, 66 million years ago (Ma). However, many aspects of their macroevolutionary trajectory remain contentious.
![dinosaur battle realm dinosaur battle realm](https://spruesandbrewsblog.files.wordpress.com/2021/04/20210416_2220061009031776377782343.jpg)
Reconstruction of the palaeodiversity of Mesozoic dinosaurs has a long tradition in palaeontology, with a growing number of studies over the last 40 years 1, 2, 3, 4, 5. We suggest that Maastrichtian North American dinosaur diversity is therefore likely to be underestimated, with the apparent decline a product of sampling bias, and not due to a climatically-driven decrease in habitability as previously hypothesised. This reduction of the spatial sampling window resulted from formation of the proto-Rocky Mountains and sea-level regression. However, a continent-wide projection demonstrates habitat stability, or even a Campanian-to-Maastrichtian increase, that is not preserved. Ecological niche modelling shows a Campanian-to-Maastrichtian habitability decrease in areas with present-day rock-outcrop. Here we combine fossil occurrences with climatic and environmental modelling to quantify latest Cretaceous North American dinosaur habitat. The latest Cretaceous (Campanian–Maastrichtian ) of North America provides the best record to address this debate, but even here diversity reconstructions are biased by uneven sampling. In the lead-up to the Cretaceous/Paleogene mass extinction, dinosaur diversity is argued to have been either in long-term decline, or thriving until their sudden demise.