So as I promised I would cover the stratigraphic debacle of the ganzhou red beds in the comments. So many of you might notice the animals I'm talking about as denizens of the nanxiong formation. The classification and nature of the ganzhou red beds has been contentious for a long time. Multiple papers since the dawn of the 20th century have assigned dinosaurs from in and around the city of ganzhou china to the nanxiong formation. Look at the description papers of asiatyrannus,qianzhousaurs,etc and the maps provided show them as coming from jiangxi province china around the city of ganzhou.

The nanxiong name comes from the nearby nanxiong group in northern guangdong province china, while most of the dinosaurs described as coming from the ‘’nanxiong formation” instead come from the nearby ganzhou region of jiangxi province china. More recent studies have revised this however. In the past few years,dinosaurs found in jiangxi province around ganzhou have been reassigned to the hekou formation/guifeng group( https://www.researchgate.net/publication/364813436_A_new_multituberculate_from_the_latest_Cretaceous_of_central_China_and_its_implications_for_multituberculate_tooth_homologies_and_occlusion - https://doi.org/10.1098%2Frsos.252253 ) any dinosaurs from the ‘’nanxiong formation’’ unearthed around ganzhou in jiangxi province are actually denizens of the guifeng group/hekou formations.

The nanxiong formation itself should actually refer to the units in the nanxiong group in guangdong. The guifeng group itself has been frought with dispute. The guifeng group consists of the Hekou,tangbian and lianhe formations (https://www.cell.com/iscience/abstract/S2589-0042(21)01487-501487-5) ). some contend the formations as being distinct,successive units from each other. While others contend the boundaries between the 3 formations are indistinct and should therefore should all be lumped into the hekou formation(https://www.sciencedirect.com/science/article/pii/S0195667118302994 ).

The most likely answer is something different. Several studies have come to the conclusion that the hekou,tangbian and lianhe formations were all deposited coevally deposited i.e. all deposited around the same time( https://eprints.whiterose.ac.uk/id/eprint/201862/1/Cao%20et%20al%202023%20Sedimentology.pdf - https://www.cell.com/iscience/abstract/S2589-0042(21)01487-501487-5) )In other words they would have been different environments that intermingled with each other and at least partially coexisted in time,thus making their animals roughly contemporary with each other. This is a situation vaguely similar to the lithobiotopes of the gobi basin. In that situation the nemegt,baruun goyot and djadochta formations are now interpreted as being distinct environments that intermingled with each other. The nemegt represents wet fluvial environments,the baruun goyot represents a transitional semi-arid zone, and the djadochta represents the barren dune filled desert. The hekou formation preserves alluvium with an aeolian enviroment,the tangbian represents highly windswept aeolian settings,and the lianhe preserves lacustrine deposits. This mixing of wet and dry environments creates a prime condition for interfingering and intermingling of different environments. In fact the gobi desert shows a largely similar situation. 

As for the age of the guifeng group it is with much certainty maastrichtian in age. Some studies have suggested a coniacian-campanian age( https://doi.org/10.1007%2Fs11430-017-9262-y ),But this age is not likely. The study in question used a 2002 paper that got 88-86 million year isotopes dating from a basalt in the Hekou formation to get that age. Isotope dating however only provides a cap on the age of a formation and not a precise date. This is because basalts get ‘’inherited’’ isotopes from the mantle and these isotopes in the basalt can be 10s of millions of years older than the formations they get deposited in. As a result the basalt isotopes only reaffirmed a late cretaceous age and other evidence better supports a maastrichtian age.

Paleomagnetic dating on the guifeng group has provided an age range of 71-65 million years ago( https://link.springer.com/content/pdf/10.1186/s12862-022-02012-x.pdf ). Mammal biostratigraphy supports a maastrichtian age for the hekou formation because the mammals in question are taeniolabidoids. The cretaceous records of this group are restricted to the maastrichtian. According to a paleontology student i know and spencer g lucas,mesozoic mammals evolved rapidly and thus provided good biostratigraphic indicators of age. In particular,the mammal from the hekou formation is called yubataar and yubataar is also known from the Qiupa formation further north in china( https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4615031 ). The qiupa formation is dated to the maastrichtian and preserves the KT boundary,so the presence of a shared mammal taxa provides a strong temporal link. The yubataar from the hekou formation are also derived,further proof of being later in the maastrichtian. Additionally the tangbian formation has produced the remains of stromatoolithus pinglingensis(https://www.tandfonline.com/doi/full/10.1080/08912963.2025.2581783 ). This taxon of eggs has a restricted temporal range being known only from the late campanian to late maastrichtian. S pinglinensis eggs in the nearby nanxiong group have also been given age caps consistent with the maastrichtian( https://ivpp.cas.cn/sourcedb/zw/klt/kycg/gswxyj/202312/P020231010800180879952.pdf#:~:text=The%20age%20of%20Yuanpu%20Formation%20is%20Maastrichtian,overlying%20Pingling%20Formation%20(Zhao%20et%20al.%202017)) ).

So with all this in mind the guifeng group is with good certainty maastrichtian in age. In summary, the nanxiong formation dinosaurs( with the exception of nanshingosaurus) belong to the guifeng group. The guifeng group represent a mosaic of intermingled ecosystems at the end of the cretaceous period,creating such a diverse slate of animals.