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I had identified this bramble colony as R. bifrons (first time seen in DFW) from photos after I found R. pascuus for the first time in the metroplex too. I couldn't wait to go see it for myself and tick off all 5 TX species on my life list!

Picture descriptions and general notes:
1 - White abaxial leaf surfaces (general pic for ID)
STEMS
2 - Primocane #1
3 - Primocane #1 close up; nearly erect prickles with broad bases, pubescent
4 - Primocane #2; retrorse prickles
5 - Cross section of primocane #1 showing pentagonal shape
6 - Floricane #1; retrorse prickles with broad bases, pubescent
7 - Floricane #1 close up
8 - Older floricanes (#2) bicolored; red on top, green on bottom
9 - Floricane #2; features consistent with floricane #1
10/11 - Floricane #2 prickles 5mm wide and 6mm long
12/13 - Primocane prickles 4mm wide and 6mm long
14 - Stems growing densely underneath leaf canopy
LEAVES
15 - Dense leafy growth
16 - Terminal leaflet; shape: oval, base: rounded, margins: serrate, apex: caudate to attenuate; surface: not lustrous
17 - Abaxial leaf surface; petioles, petiolules, and primary veins armed; secondary veins and blade unarmed
18 - Petiole
19 - Terminal petiolule
20 - Primary and secondary veins
21 - Abaxial leaf blade white tomentose
22 - Stipules very long and narrow; Axillary bud present
23 - New leaves appear more corrugated and shinier than older leaves which are duller, less corrugated, and wider
24 - Several leaves with misshapen leaflets, or even a single oversized leaflet
GROWTH/HABIT
25 - New growth creeps along the edges, could be mistaken for vining/low habit
26 - 5 Leaflets on creeping floricanes more consistent than shrubby sections
27 - General growth habitat; between the bank of a creek and a concrete pathway; Full sun; This particular section was typically 4 ft high
28 - R. bifrons growing closest to path, with Cornus drummondii closest to the creek bank; Other nearby vegetation includes Celtis laevigata, Maclura pomifera, Salix nigra, Bothriochloa ischaemum var. songarica, Paspalum dilatatum, Calyptocarpus vialis
29 - Trying to estimate plant height using an isosceles right triangle based on the 6 foot wide path. Plants average 4-6 feet (12-18 dm)
30 - This particular colony of R. bifrons measured 166m along the edge
31 - Even when soil was scarce, the creeping canes would still spread thickly over the rocky ground.
32 - Soil along creek was clay over limestone
33 - USGS map indicates soil content: Thick clay units and thin limestone units alternating clay, marl, and limestone

Additional observations:

-- My first impression was this is the thickest growth, both in floricanes and leaf coverage, of any of the upright species. In heavy shade (under trees) the growth was not as thick or as tall. Probably the biggest colony of Rubus I've seen.
-- Several leaves had misshapen lateral leaflets, or a single leaflet, (1-)3-5 leaflets overall.

-- No prior season inflorescences seen at all. Nothing remaining on the stems or on the ground. (R. pascuus still has inflorescences attached at this time.)

Part of a HUGE infestation; there were several patches on “islands” in the middle of the creek, and very dense patches along the creek bank. Zoomed out shots show the extent of the largest dense patch; it covers more than an acre of land easily.

Visiting as follow up to reports by @inarticulate. Can confirm all their notes. Also, these photos would look even worse but someone cut the tops of hundreds of plants off, pulled many, too. I would estimate that there are many thousands of fumeworts here. A very tiny percentage of the seed pods have started to explode when touched.
In the 2nd photo you can see the bluebells and the area between the bluebells. That stuff in between the bluebells is mostly incised fumewort.
Post script: I've added two more photos and arranged them to show the walk down an ~50 ft long side-path immediately upstream of dam. #1: At entrance to the path, the native spring ephemerals, mostly bluebells, look fine and there's no noticeable fumewort. #2: A few feet further and you can see individual fumeworts among the native spring ephemerals. #3 #4: At the end of the path large percentages of bluebells/natives are being displaced. All that area in between the bluebells is fumewort. It would be easier to see in the photo but a volunteer (whom I had not met yet) had cut the tops off all the fumeworts!